BackGround Papers 740839

TRL Limited APPLICATION GUIDE 49 (Issue F) ARCADY 6 USER GUIDE (for drive-on-the-left) by James C Binning © Copyright TRL Limited 2004. All rights reserved.

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TRL Software Bureau Crowthorne House

Nine Mile Ride Wokingham, Berkshire

RG40 3GA United Kingdom

Tel: +44 (0)1344 770758 Fax: +44 (0)1344 770864

E-mail: [email protected] www.trlsoftware.co.uk

SoftwareBureau

The information contained herein is the property of TRL Limited. Whilst every effort has been made to ensure that the information presented in this Application Guide is relevant, accurate and up-to-date at the time of publication, TRL Limited cannot accept any liability for any error or omission. First Published 2004 ISSN 1365-6929 Windows XP and Windows VISTA are registered trade marks of Microsoft Corporation. Other products and company names mentioned herein may be the trademarks of their respective owners.

ABSTRACT OF APPLICATION GUIDE 49 2004 ARCADY 6 (Assessment of Roundabout CApacity and DelaY Version 6) is the latest version of the internationally-recognised computer program for predicting capacities, queue lengths and delays (both queueing and geometric) at non-signalised roundabouts and mini-roundabouts. It can also be used to predict accident frequencies or indices for a particular layout from information about traffic flow and site data. The program is used as a tool by junction design engineers to help them to assess their designs. It is used primarily for modelling peak periods and can be applied to any single-island roundabout with three to seven arms and any mini-roundabout with three or four arms. ARCADY can model junctions in countries where drivers drive on the left or the right – This application guide is specifically for those countries where drivers drive on the left-hand-side of the road (i.e. ‘drive on the left’). An alternative application guide (AG50) for ‘drive on the right’ countries is also available. The ARCADY 6 user guide describes all the features this new version of the program has to offer which includes a variety of analysis improvements such as a new Pelican Crossing model for both standard and mini-roundabouts and the reporting of the estimated delay for arriving vehicles within a given time period. Other major changes to ARCADY include the ability to produce customisable reports with embedded graphics, completely new graphical analysis options, multiple demand flow sets, and various new user interface features such as filename history, revised queue animations, and a revised context-sensitive help system. Other topics in the guide include a description of the theory and research incorporated in ARCADY, how an ARCADY model should be specified and the way data is entered using its graphical user interface (including guidance on how to measure data). Also described is the output and how it should be interpreted. A number of examples have been included to aid the understanding of different roundabouts and the modelling problems they pose.

ARCADY 6 user guide 13th June 2008, Issue F For program advice, sales and distribution information contact:

The TRL Software Bureau Address:

TRL Limited Crowthorne House Nine Mile Ride WOKINGHAM Berks RG40 3GA United Kingdom

------------------------------------------------------------------------------------------- Telephone lines: +44 (0)1344 770758 +44 (0)1344 770176 +44 (0)1344 770558 Fax: +44 (0)1344 770864 Email: [email protected] Web Address: http://www.trlsoftware.co.uk -------------------------------------------------------------------------------------------

If you wish to receive regular information (by email) about this product and other TRL software products you can subscribe to TRL’s free ‘Software Bulletin’ (Ezine) via our web site. This includes maintenance update information, articles on new releases, frequently asked questions (FAQs), and information on training courses available. This publication supplements ‘Traffic Software News’, our quarterly newsletter, that is distributed to maintenance holders.

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Chapter headings

1 Introduction ........................................................................................... 1

2 Installation and hardware requirements ............................................ 7

3 Theory and Research .......................................................................... 11

4 Additional Theory for the Program Options.................................... 17

5 Operation of the Analysis Program................................................... 39

6 Graphical User Interface (GUI) Operation ...................................... 47

7 Data Input ............................................................................................ 93

8 The Output and its Interpretation................................................... 143

9 Modelling Special Situations ............................................................ 179

10 Acknowledgements............................................................................ 181

11 References .......................................................................................... 181

APPENDICES........................................................................................... 185

INDEX........................................................................................................ 246

Contents i

Contents 1 Introduction ...........................................................................................1

1.1 About ARCADY.......................................................................................................1 1.2 Changes and Improvements in ARCADY 6 .............................................................2 1.3 About this manual .....................................................................................................5 1.4 Help Files ..................................................................................................................5 1.5 Drive-on-the-left and Drive-on-the-right ..................................................................6

2 Installation and hardware requirements ............................................7

2.1 Hardware requirements .............................................................................................7 2.2 Supplied programs and associated files ....................................................................7 2.3 Installing the software ...............................................................................................7 2.4 Copy-protection and software registration................................................................8 2.5 Checking the installation...........................................................................................9

3 Theory and Research ..........................................................................11

3.1 About this chapter ...................................................................................................11 3.2 Principles of the program........................................................................................11 3.3 Junction design in general.......................................................................................11 3.4 Entry Capacity/Circulating Flow relationship ........................................................12 3.5 Interaction between arms ........................................................................................14 3.6 Time-dependent queuing theory .............................................................................15 3.7 Entry width caution .................................................................................................15 3.8 Stream labelling and conventions ...........................................................................16

4 Additional Theory for the Program Options ....................................17

4.1 About this chapter ...................................................................................................17 4.2 Day-to-day variability of queues.............................................................................17 4.3 Geometric delays.....................................................................................................18 4.4 Accident prediction .................................................................................................19 4.5 Pedestrian crossings ................................................................................................21 4.6 Site-specific capacity corrections............................................................................22 4.7 Grade-separated or very large junctions .................................................................23 4.8 Marginal effects analysis.........................................................................................24 4.9 Demand flow options ..............................................................................................26 4.10 Turning proportions ................................................................................................34 4.11 Heavy vehicle percentages ......................................................................................35 4.12 The effects of lighting and surface conditions ........................................................35 4.13 Point-to-point journey times ...................................................................................36

5 Operation of the Analysis Program...................................................39

ii Contents 5.1 About this chapter................................................................................................... 39 5.2 Queue-length/delay calculations ............................................................................ 39 5.3 The procedure in detail ........................................................................................... 40 5.4 Numerical accuracy ................................................................................................ 42 5.5 Files associated with ARCADY 6.......................................................................... 43 5.6 Queue variability .................................................................................................... 44 5.7 Site-specific data (observed flows / intercept correction) ...................................... 45

6 Graphical User Interface (GUI) Operation ...................................... 47

6.1 About this chapter................................................................................................... 47 6.2 Main menu system.................................................................................................. 47 6.3 Main Toolbar .......................................................................................................... 48 6.4 Keeping track of data-entry .................................................................................... 50 6.5 Data-entry windows functionality .......................................................................... 51 6.6 Running the analysis program................................................................................ 52 6.7 Batch processing of data files................................................................................. 53 6.8 Saving and retrieving input data files..................................................................... 53 6.9 Specifying output analysis files.............................................................................. 57 6.10 Junction diagram..................................................................................................... 57 6.11 Animation of queues............................................................................................... 60 6.12 Running the Report Designer ................................................................................. 61 6.13 Report Viewer......................................................................................................... 71 6.14 Running the Graph Designer .................................................................................. 75 6.15 Viewing ARCADY text files.................................................................................. 78 6.16 Printing ASCII text................................................................................................. 82 6.17 Exporting output data ............................................................................................. 83 6.18 User Options ........................................................................................................... 83 6.19 Help system ............................................................................................................ 89 6.20 Leaving ARCADY ................................................................................................. 91 6.21 Error messages........................................................................................................ 91

7 Data Input ............................................................................................ 93

7.1 About this chapter..................................................................................................... 93 7.2 General data-entry conventions................................................................................ 94 7.3 Getting started........................................................................................................... 95 7.4 Run Information ....................................................................................................... 95 7.5 Parameters ................................................................................................................ 96 7.6 Junction type and arm names ................................................................................... 97 7.7 Demand type (principal options) .............................................................................. 99 7.8 Principal options....................................................................................................... 99 7.9 Geometries, queues and capacities ......................................................................... 105 7.10 Arm geometries .................................................................................................... 105 7.11 Circulating flow and separation (CIRFLO and SEP)........................................... 109 7.12 Pedestrian crossing and demand type................................................................... 110

Contents iii

7.13 Geometric delay data.............................................................................................111 7.14 Distances through junction (“Delay 2”)................................................................113 7.15 Site-specific observed flows .................................................................................114 7.16 Site-specific correction terms................................................................................115 7.17 Queue length variations ........................................................................................116 7.18 Vehicle flow data (demand data) ..........................................................................117 7.19 Turning proportions (demand data) ......................................................................124 7.20 Heavy vehicle percentages (demand data)............................................................125 7.21 Pedestrian crossing data ........................................................................................126 7.22 Accident prediction for standard roundabouts......................................................129 7.23 Simple Accident prediction for mini-roundabouts ...............................................133 7.24 Full Accident prediction for mini-roundabouts ....................................................136

8 The Output and its Interpretation ...................................................143

8.1 About this chapter ...................................................................................................143 8.2 Characteristics of the output/Output overview .......................................................143 8.3 Output to the screen ................................................................................................144 8.4 Junction assessment data – capacity, queues and delays ........................................144 8.5 Junction assessment data - accident prediction.......................................................165 8.6 Error messages ........................................................................................................173 8.7 Examples .................................................................................................................177 8.8 ASCII (.VAO) output results file............................................................................178

9 Modelling Special Situations ............................................................179

9.1 About this chapter ...................................................................................................179 9.2 Entry-only and exit-only arms ................................................................................179 9.3 Motorway-type slip roads ......................................................................................179 9.4 The treatment of filter lanes ....................................................................................179 9.5 Double-island roundabouts .....................................................................................180 9.6 Other special situations ...........................................................................................180

10 Acknowledgements............................................................................181

11 References ..........................................................................................181

APPENDICES ...........................................................................................185

Appendix A - Card image format of data ......................................................................187 Appendix B - Measurement of the geometric parameters affecting capacity................215 Appendix C - Measurement of the geometric delay parameters....................................223 Appendix D - Site-specific measurements for capacity correction ...............................227 Appendix E - Measurement of “Queue Marker” position .............................................229 Appendix F - Measurement of pedestrian crossing geometry .......................................231 Appendix G - Measurement of accident prediction geometry.......................................233 Appendix H - Estimation of circulating flow (CIRFLO)...............................................239

iv Contents Appendix J – Glossary................................................................................................... 241

INDEX........................................................................................................ 246

Introduction Page 1

1 Introduction 1.1 About ARCADY ARCADY 6 (Assessment of Roundabout Capacity and Delay Version 6) is a computer program for predicting capacities, queues and delays at roundabouts and mini-roundabouts. It can also predict accident frequencies and geometric delays. All of these predictions can be used in testing design options both for new roundabouts and modifications to existing ones. Another possible use is for examining the changes in queues and delays at existing roundabouts when the level or balance of traffic demand changes, perhaps due to changes in routeing patterns following improvements in the highway network. The program is also able to predict the daily variability of queues. Single-island roundabouts with between three and seven arms can be modelled, including grade-separated roundabouts. The program will normally be used to model peak periods, but any period (up to 24 hours) can be investigated. Mini-roundabouts with either three or four arms can be modelled, as long as the central island diameter is not greater than four metres and there is no street furniture in the centre of the junction. ARCADY 6 is the latest evolution of the ARCADY program, which originated, in its batch version, in 1981. ARCADY is closely related to programs PICADY (which models major/minor priority junctions) and OSCADY (which models isolated, traffic signal controlled junctions). It must be stressed that all of these programs are intended as aids in the design of junctions and are not intended to cover all aspects of design. In recognition of this, the manual contains advice on the accuracy and interpretation of the results; it also describes warnings generated by the program and refers the user to other related publications where necessary. ARCADY, PICADY and OSCADY are concerned only with the operational performance of individual junctions. For the overall appraisal of wider based road schemes, an economic evaluation will be required, and this can be achieved by use of the Department of Transport’s cost-benefit analysis program COBA (UK Department for Transport et al).

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1.2 Changes and Improvements in ARCADY 6 This section allows existing users of ARCADY 5 to quickly familiarise themselves with what has changed and what new facilities have been added to ARCADY 6 by summarising the changes and improvements. Full descriptions of the changes and how to use the new features are to be found in the other chapters. 1.2.1 Report Designer

A report designer allows user-defined reports to be created. These can include embedded graphs, junction diagrams, queue snapshots and additional annotation. Clearer versions of the standard tables from the ARCADY output file (*.VAO) can be included or excluded from a report and put into any order. Furthermore, the headers and footers of the reports are fully customisable. All the features listed plus several more, eliminate the need to use any other Windows applications to produce clear and concise professional-looking reports. 1.2.2 Printing

ARCADY offers improved printing facilities. The Report Generator allows user- defined reports to be printed using a choice of electronic formats, including HTML. 1.2.3 Graph Designer

ARCADY’s enhanced analytical capability includes a new graphical reporting system. A Graph Designer allows user-defined graphs to be generated by plotting one parameter against another over a defined range of values, e.g. capacity against entry width. The graphs can also be incorporated into the graphical reports produced by the Report Designer. 1.2.4 Queue Animation

The display of queue lengths on a schematic of a roundabout has been enhanced to provide a more accurate (recognisable) representation of the junction being modelled, e.g. geometric features such as the angles between arms can now to be specified so that the junction resembles the real junction. The diagram can be included in the graphical report produced by the Report Designer. 1.2.5 Pelican Crossing Model

ARCADY has a new, more accurate, Pelican Crossing model which can be applied to both standard roundabouts and mini-roundabouts. By specifying full details of the operation of a Pelican crossing, users can now achieve improved results when compared to the existing ARCADY 5 Pelican Model. In addition, it is now possible to model Pelicans at standard roundabouts.

Introduction Page 3

1.2.6 Arriving Vehicle Delay

The output of ARCADY has been enhanced by the addition of the prediction of the delay experienced by an average vehicle arriving during a particular time period. Previously, only the average delay per vehicle for the whole modelled period has been available. 1.2.7 Multiple Demand Sets

Users can store, select and sum multiple demand sets (up to a maximum of 9). This feature provides the opportunity to store ‘background’ flows along with ‘additional’ flows associated with a variety of scenarios. Selected demand sets are summed prior to an analysis run. 1.2.8 Point-to-point Journey Times

PICADY now calculates point-to-point journey times through the junction (from each approach to all exits. The distance upstream and downstream of the junction over which the journey times are calculated, are defined by the user. 1.2.9 Units of measure and terminology

In recognition of the usefulness of ARCADY in a variety of locations outside of the UK geometric data can now be entered in either metric units (as before) or in US customary units (i.e. ‘feet decimal’ can be used instead of metres). The new Report Designer is fully compatible with both units. The user can also re-define certain terminology used by the program. 1.2.10 New TRL VIEWER program (Version 3)

The latest version of the TRL VIEWER program (Version 3) is supplied with ARCADY 6. The following improvements have been made to it since Version 2:

• Improved file comparison facilities: - Selection comparison added - Enhanced synchronised scrolling, providing a choice of up/down (by 5

lines), match by ratio, and match by line number - Locking windows - Go to next difference

• recognises the DfT’s COBA 11 (*.PRN) and QUADRO 4 (*.PRS) results files in addition to the results files produced by all versions of ARCADY, PICADY, OSCADY and TRANSYT.

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1.2.11 Other features of ARCADY 6

The following is a list of some of the other new features of ARCADY 6:

• Modernised graphical interface • File history list • Traffic demand data scaling factors for each arm • Automatic retention of observed site-specific flow data • Importing of ARCADY 4 and ARCADY 5 data files • Fully revised program documentation (context-sensitive help system, and

Application Guide)

Introduction Page 5

1.3 About this manual The coverage of this manual is comprehensive and is intended for anyone who is likely to be involved with the use of ARCADY. It is hoped that new users will quickly understand the program by reading, and by reference to, this manual. To achieve these aims, this manual describes, in separate chapters, the theory and research incorporated in ARCADY, how an ARCADY model should be specified (including guidance on how to measure data) and how the data is entered. Also described is the output and how it should be interpreted. A number of examples have been included to aid in the understanding of individual junctions and the modelling problems they pose. Each chapter has a section entitled “About this chapter” which outlines the contents. Whilst it is desirable to read as much of each chapter as possible, it is accepted that sufficient time will not always be available. Hence guidance is given on which sections to read prior to using ARCADY to model a junction for the first time. The following icons are used throughout the manual to highlight relevant points about the topic being covered.

is used to emphasise important points;

is used to warn of the consequences of doing something wrong;

is used to highlight features in ARCADY 6 that are new to ARCADY

is used to highlight differences between modelling a standard roundabout and a mini-roundabout;

In many places it is inevitable that “jargon” will have been used, particularly when talking about features relating to the Windows implementation. To help avoid repeated explanation of such words a glossary of terms is included in Appendix J, page 241. 1.4 Help Files The complete ARCADY 6 manual has been translated into a standard Windows help file with hyper-text, browse buttons, and search facilities. This allows context-sensitive help

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to be available throughout the program, making referrals to the appropriate ARCADY help file fast and efficient. ARCADY 6 also has a “Help Tips” help file that contains additional useful information about the software. It includes information on the differences between the current version and the previous one; details on any new features introduced in subsequent releases, and contact information for the TRL Software Bureau. It also includes a particularly useful FAQ (frequently asked question) section which gives advice on particular aspects of the program that warrant special consideration, such as difficult design considerations or program nuances. Additional up-to-date support information is also available from the Support section of our web site at www.trlsoftware.co.uk 1.5 Drive-on-the-left and Drive-on-the-right This product can model both drive-on-the-left and drive-on-the-right situations. The program can be switched from drive-on-the-left (e.g. UK) to drive-on-the-right (e.g. mainland Europe and North America) in the following two ways: • Open an existing data file – the program will switch automatically to the correct

orientation for that file. • from the Main Menu select Options/User Options/Drive on the right for drive-on-

the-right situations and leave blank for drive-on-the-left situations.

REFER TO YOUR PRODUCT LICENCE AGREEMENT FOR DETAILS OF THE TERMS AND CONDITIONS OF USE OF THIS PRODUCT. ANY UK/INTERNATIONAL RESTRICTIONS OF USE WILL STILL APPLY. YOU MUST STILL BE LICENCED TO USE THIS PRODUCT IN THE COUNTRY IN WHICH IT IS BEING USED.

ARCADY is predominantly an empirical model based on UK data. For use outside of the UK the appropriateness of the model should be checked by the user.

http://www.trlsoftware.co.uk/

Installation and hardware requirements Page 7

2 Installation and hardware requirements

2.1 Hardware requirements Minimum recommended hardware and software requirements as follows:

• A PC with a 500MHz processor or faster. • A mouse • Windows XP/VISTA. • A colour monitor capable of displaying 16-colours in 800x600 video mode

(ideally, 1024x768 video mode). • A minimum of 40 MB available hard disk space.

2.2 Supplied programs and associated files At the time of writing ARCADY 6 is supplied on CD. For an up-to-date list of the files supplied, version numbers, and release dates please look at the file RELEASE.TXT. Another file, README.TXT, gives further information about recent changes and updates to the program. Information on any new features and how to use them is also included in the Help Tips help file (section 6.19.2, page 90). 2.3 Installing the software The ARCADY 6 files are supplied in compressed form. To install the software you must run Windows first then run the program called SETUP.EXE.

To install from CD-ROM:

• Insert the CD-ROM. • Click on the Start menu, and choose Run... • Type X:\SETUP (where X is the drive letter of your CD-ROM drive) and press

Return. If the SETUP program is not found, explore the CD for SETUP.EXE.

During installation, which takes approximately 3 minutes or less, you will be asked to name the drive and directory you wish to install ARCADY to. All of the ARCADY executables will be copied into the specified directory, including the Viewer program (VIEWER.EXE), the analysis program (ARCADY6.EXE), GUI (VARCADY6.EXE) and other associated files. The installation program automatically decompresses the files as they are copied to their respective subdirectories. Note: Some files are copied to your Windows “System”

Chapter 2

subdirectory. A list of all the supplied files and their locations is given in the RELEASE.TXT file supplied on the CD. During the installation process the menu “Programs\ARCADY 6” is added to the START Menu with several items within it, including “ARCADY 6” and “VIEWER”. 2.4 Copy-protection and software registration ARCADY is a copy-protected software product. Having installed ARCADY it will initially run in a ‘DEMO’ mode and in order to use the full product you must register it with the TRL Software Bureau.

2.4.1 Stand-alone version

Each installation of the stand-alone version of this software product must be registered. Full setup instructions are available in the file “security.doc” or ““SOFTWARE REGISTRATION.PDF” provided with the software.

This document includes instructions on how to transfer your registered product from one PC to another. Read these before you lose access to your old PC!

Depending on the situation, it is also possible to upgrade licences. This usually happens when purchasing the full version of a product after previously leasing it. In this situation the software licence can be upgraded. Again, see the file “Security.doc” or ““SOFTWARE REGISTRATION.PDF” ”for full instructions. 2.4.2 Network copy-protected (concurrent licence) version

The network copy-protected (concurrent-use) version of this software product is designed to allow the software to run provided the number of current users has not yet reached the allowed limit of concurrent users. Having installed this version of the software it will initially run in a ‘DEMO’ mode and in order to use the full product you must setup the software as a Network Client. Full setup instructions are available in the file “security net.doc” or “SOFTWARE NETWORK REGISTRATION.PDF” provided with the software.

Installation and hardware requirements Page 9

2.5 Checking the installation Once the installation is complete you may wish to check that it has been done successfully. In order to do this carry out the following: i) Run ARCADY from the START Menu or using the ‘RUN’ command. ii) Load the example file SAMPLE1.VAI iii) Run the ARCADY model . Compare the output file created (SAMPLE1.VAO) with the supplied file SAMPLE1A.VAO using either the VIEWER program, a text file comparison utility or import it into a word-processor and compare the files there.

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Theory and Research Page 11

3 Theory and Research 3.1 About this chapter This chapter describes the theory and research incorporated in ARCADY 6. In particular, it outlines the theory of roundabout capacity and the use of time-dependent queuing theory. These are fundamental to ARCADY. It is intended as an overview covering the detail required by traffic engineers to assist them in getting the best out of ARCADY. Those wishing to know more about the theory should obtain the documents referenced. 3.1.1 Quick start

This subsection gives advice on which sections should be studied before starting to use ARCADY. The amount of study required depends on the level of familiarity with both ARCADY and traffic engineering practice. Those familiar with ARCADY 4 or earlier can skip all of chapter 3 except for section 3.4 which contains information relating to the mini-roundabout theory and research introduced in ARCADY 5. Those familiar with ARCADY 5 can skip to chapter 4.

Those with no traffic engineering experience should not really be tackling junction design and assessment without at least some training and/or the assistance of others with some traffic engineering experience (Contact TRL for details of the training courses available).

3.2 Principles of the program The program uses empirical formulae for calculating the capacity of each entry arm as a function of the circulating flow crossing in front of the entry. The operation of the roundabout as a whole is calculated on the basis that the entries to the roundabouts are linked by the common circulating carriageway. Queues and delays are calculated using time-dependent queuing theory. The method treats the whole range of demand and capacity and takes proper account of the statistical nature of traffic and of the variations with time of demand and capacity. 3.3 Junction design in general As mentioned above, ARCADY is to be used as an aid in achieving good design, and it must be stressed that factors additional to those required for input to the program will need to be taken into account in roundabout design, for safety and convenience of operation. Factors to be considered include:

i) Entry width and deflection criteria.

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ii) Crossfall and drainage. iii) Space requirements for heavy flows of heavy vehicles. iv) Standards of visibility.

Other important factors include: v) Road User specific requirements (e.g. Pedestrians and Cyclists) vi) Roundabout type vii) Lighting provision. viii) The use of signs, markings and road furniture. ix) Surface characteristics x) Circulatory carriageway design/speeds xi) Segregated left-turning lanes xi) Aesthetic considerations (e.g. landscaping).

The current Departmental Standard TD16/93 (Department of Transport, 1993) (DMRB 6.2) quantifies geometric aspects of items (i) to (iv) above and includes detailed general guidance on the other items. Guidance on the most appropriate form of junction is given in TA23 (DMRB 6.2) and TA30 (DMRB 5.1). 3.4 Entry Capacity/Circulating Flow relationship The first fundamental feature of ARCADY is the equation relating the entry capacity to circulation flow for roundabouts. For standard roundabouts, this is formulated in LR942 (Kimber, 1980). as: Qe = Fi - fi Qc ............................................... (1) where Qe = entry capacity Qc = circulating flow

Fi and fi (i.e. the intercept and slope respectively) are constants determined by the geometric characteristics.

The detailed formulae for Fi and fi are presented in the summary to LR942. The geometric features which affect the values of Fi and fi are illustrated in Appendix B (page 215) and listed as follows:


i) v approach road half-width (metres) ii) e entry width measured along the normal to the nearside kerbline (metres). iii) l' average effective length over which the flare is developed (metres). iv) r the entry radius measured as the minimum radius of curvature of the

nearside kerbline at entry (metres). v) D inscribed circle diameter (metres).

vi) φ the entry angle in degrees (geometric proxy for the conflict angle between

entering and circulating streams).

It must be emphasised that the ARCADY model for standard roundabouts has been calibrated only over the range of junction geometries included in the LR942 study. It follows, therefore, that there is an increasing risk of unreliable results, due to extrapolation, as junction designs or individual geometric parameters extend beyond this range. Of the geometric parameters determining entry capacity, all but the flare length (l') have limits built into the program. The research data included flare lengths up to 27 metres, and it is suggested that values extending beyond 30 metres should be treated with increasing caution.

Details of the capacity relationships for mini-roundabouts are yet to be published, so cannot be quoted here.

The research identified three main geometric features which affect the intercept and slope (illustrated in Appendix B, page 215). These are shown below: i) K entry corner kerb line distance (metres) - distinguishes entries

that are further than usual from the next arm clockwise.

ii) e effective entry width (metres).

iii) G50 approach gradient over 50 metres (metres).

Mini-roundabout analysis would also suffer the risk of unreliable results if junction designs or individual geometric parameters are extended beyond the range to which the model is calibrated. Therefore suitable limits are built into the program to help prevent this happening.

Chapter 3

3.5 Interaction between arms The second fundamental feature of ARCADY is the way in which flows from individual arms of a roundabout are linked. This applies equally to standard roundabouts and mini-roundabouts. The circulating flow across any entry, QC , is derived from the entry flows and turning proportions from previous arms. As an example, Figure 3-1 shows the components of circulating flow across arm A of a 4-arm roundabout. In this case:

QC (circulating flow) = pCB x (entry flow from arm C) + (pDB + pDC) x (entry flow from arm D). where

pCB = the proportion of traffic from arm C going to arm B, etc.

The circulating flows across other arms are derived similarly.

Figure 3-1 Components of the circulating flow Qc at arm A of a four-arm

roundabout


3.6 Time-dependent queuing theory The third fundamental feature of ARCADY is time-dependent queuing theory which, because of the time-varying nature of traffic flow, is used to calculate queue-lengths and delays. The more conventional queuing theories, namely “steady-state” and “deterministic” are particularly unsatisfactory when traffic demand lies approximately in the region 0.8-1.1 times capacity. Steady-state theory is only acceptable when the traffic intensity is below this region, and deterministic theory is suitable when traffic intensity is above this region. Time-dependent queuing theory treats all regions of traffic intensity by means of a technique based on probabilistic theory. For computational efficiency the program uses a mathematical transformation which gives very similar results to the direct application of probability theory. The method is reported in LR909 (Kimber and Hollis, 1979). 3.7 Entry width caution ARCADY assumes that the relationship between the width of an entry and its capacity is continuous - i.e. it is not dependent on the number of lanes; it has been demonstrated that entry width is the best predictor of capacity. However, the method assumes that all of the entry width will be used as long as there is a queue. There are cases where that assumption does not hold. Two of these are:

i) Where there is entry starvation, due to a little-used, dedicated left-turn or right-turn lane. For methods of dealing with such lanes see section 9.4, page 179.

ii) Where the roundabout exits are the limiting factor in determining capacity.

Again, ARCADY assumes that all of the entry width is usable to good effect - this would not be the case when exits impose a capacity restriction. The onus is on the roundabout designer to ensure that exits have adequate capacity. This may not always be practical and suitable adjustments to the ARCADY model must be made. One typical case is a 3-arm roundabout where, say, 90% of approach flow on one arm turns right. If the exit is only one lane, then vehicles will tend to queue in only one lane to avoid exit merging problems.

It should be borne in mind that there are other less obvious reasons why drivers may not use all of the available entry width, and a suitable adjustment to the input value of roundabout geometry must be made in such cases.

The results of recent extensive research into capacities at mini-roundabouts showed no evidence to support the separate modelling of different movements at multi-lane entries.

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3.8 Stream labelling and conventions The labelling procedure adopted for a roundabout is shown in Figure 3-1. In drive-on-the-left mode arms are labelled clockwise A, B and C, where arm A is usually the first arm clockwise from 12 o’clock (but not at 12 o’clock). For drive-on-the-right mode the arms are labelled in a counter-clockwise direction starting with the first arm anti-clockwise from 12 o’clock.

Additional Theory for the Program Options Page 17

4 Additional Theory for the Program Options 4.1 About this chapter This chapter describes additional theory relating to runs of the program where the user wishes to incorporate a specific feature (such as a pedestrian crossing) or to use a particular option (for example, the calculation of geometric delays). It is not essential that the user reads this section fully before running the program, unless it is necessary to incorporate one of the described features in the program run. It is necessary, however, to select one of the available options for defining demand flows (Section 4.9, page 26). 4.2 Day-to-day variability of queues The basic calculations performed by ARCADY are of mean queues and delays expected at a particular time of day, averaged over many occasions. Although these calculations are generally relevant to an economic appraisal of a particular junction scheme, there are many situations when more information is desirable. For example, the user might wish to know how often a queue will block back to another junction or fire station exit. Mean daily queues will not provide this information - what is really required is the cumulative distribution of queue-lengths. ARCADY incorporates an optional facility for estimating the distribution of queue-lengths. The calculations are based on a knowledge of the development of mean queues through time, and also a derivation of time-dependent variance of queue-length. The method is reported in detail by Kimber, Daly, Barton and Giokas (1986). The calculation of queue-length distributions allows the user of ARCADY, as an additional option, to set up a “queue marker” on any or all approaches. This marker will be positioned at some point where the queue is deemed to have reached a critical point (say, when it starts to block another junction). The output from the program will then report the probability of the queue reaching back to the queue marker or beyond, for each time segment of the period modelled (the average vehicle length plus the distance to the next vehicle is assumed to be 8.5 metres). This probability can be translated into the number of days per year that the queue will reach the marker. In determining the probability of reaching a queue marker, the program takes account of multiple stream queuing on the assumption that each stream requires a minimum of 2.8 metres road width.

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4.3 Geometric delays Vehicles often have to slow down to negotiate a junction, even in the absence of other traffic. The resulting delay, which is associated with the layout of the junction, is called geometric delay, and is the sum of three components:

i) time lost decelerating and accelerating

ii) time lost due to slower speeds through a junction

iii) time lost due to longer distances through a junction

In general, geometric delays increase with the size of the junctions and with the proportion of turning traffic, left-turners being subject to less delay than right-turners. Delay is determined as an “extra” journey time over a “no-junction” alternative. The geometric delay associated with each turning movement is calculated from geometric parameters using the formulae reported in SR 810 (McDonald, Hounsell and Kimber, 1984). The geometric delay experienced by vehicles entering the junction from any arm is calculated by summing their individual delays, and totals are thus obtained for each time segment and for the complete modelled period. The deceleration rate when approaching a junction and the acceleration rate after leaving it are calculated from the arm speeds, VA and VD (measured at a point on the arm beyond the influence of the junction), and the speed through the junction. For any movement, the junction speed is calculated using the following data:

- entry and exit angles (ENA and EXA) - entry and exit radii (r and EXR) - visibility distances (SD) - inscribed circle diameter (D)

of the roundabout - types of turn

The types of turn considered are left-turn, straight-ahead with a little deflection on the path through the junction, straight-ahead with a significant deflection, and right-turn. To determine the type of turn, the angle between successive arms must be provided. The distances from junction entry to junction centre, D1, from centre to exit, D2, and the distance travelled through the junction, DBC, are also required for calculation of the


delay due to travelling extra distance. The values of delay thus calculated for each turning movement are appropriate for light vehicles and are increased by 15 per cent for heavy vehicles to reflect their lower deceleration and acceleration rate. For movements at a grade-separated or large roundabout the geometric delay is reduced because of the higher acceleration rates. The method of measuring the geometric parameters referred to above is given in Appendix C, page 223.

ARCADY does not calculate any geometric delay values for mini-

roundabouts.

4.4 Accident prediction The number of personal injury accidents per year at four-arm at-grade roundabouts may be estimated using formulae derived by research and reported in LR 1120 (Maycock and Hall, 1984).

The number of personal injury accidents per year can also be calculated for mini-roundabouts using formulae derived by research and reported in TRL Report 281 (Kennedy, Hall and Barnard, 1998). ARCADY makes use of two of the models in this report:

(i) A model (M0) which predicts accident frequencies from flow data (with one or two other parameters).

(ii) A model (M2) which predicts accident frequencies from junction features and geometry, in addition to flow data. Naturally, this second model will give a more accurate prediction, but at the expense of having to provide more information.

The accident frequencies are calculated and displayed separately for various accident categories. The total is deduced by the summation of the individual categories. ARCADY displays the total accident frequencies for vehicles and pedestrians, entering/circulating traffic, approaching traffic, single-vehicle and other vehicle. Accident ‘frequencies’ are not calculated for standard roundabouts that are not four-arm at-grade types, because these were not represented in the LR 1120 study and may behave differently. However, providing they have a central island diameter greater than or equal to 4 metres (i.e. they are not mini-roundabouts) accident ‘indices’ are estimated. The program derives an index by relating the accident frequency that would have been calculated by the LR 1120 formulae to the mean accident frequency of all the junctions studied in LR 1120 - this mean is arbitrarily assigned an index of 1.0. It is important to

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note that for roundabouts of this type, the accident index does not give any indication of the absolute accident frequency of a particular junction because, as already mentioned, the LR 1120 formulae implicit in the derivation of the index may not be fully representative of these junctions. It is, however, reasonable to suppose that the index will provide an indication of the relative safety of one layout versus another at a particular junction - this is the only purpose of the index. Accident frequencies or indices are calculated for each arm as a function of traffic flows, percentages of motorcycles, geometric characteristics of the junction and geometric characteristics of the arm under consideration on the approach to the junction.

The accident frequencies calculated are those expected in the UK, and are not necessarily appropriate for other countries. Therefore, the accident frequencies calculated (and displayed as such) by ARCADY should be regarded as indices when used to model junctions outside the UK.

4.4.1 Traffic data requirements for accident prediction

Traffic flow data (turning counts in thousands of vehicles) are required either in the form of AADT flows which are entered directly, or traffic counts which are used to estimate the AADT flows. The traffic counts must be for a 16 hour period (0600-2200) or 12 hour period (0700-1900) on a Monday, Tuesday, Wednesday or Thursday (but not a Public Holiday) during April, May, June, August, September or October. To model any roundabout, counts are required for both total traffic flow and total number of motorcycles. For mini-roundabouts the program requires, in addition, the proportions of buses, and cycles. The input data is scaled according to the month of the count and the site “type” (i.e. urban, recreational/inter-urban or recreational) using the “E” and “M” factors given in Section 4.9 of the COBA9 manual (Department of Transport, Assessments Policy and Methods Division, 1981). The traffic data is entered in the form of entry, exit and circulating flows for each arm. The analysis of marginal effects on accident frequencies is dealt with in section 4.8, page 24.

If the user wishes to use the scaling factors as defined other versions of COBA, e.g. COBA11 (DEPARTMENT FOR TRANSPORT et al, 2001) they will need to calculate the AADT flows manually.


4.5 Pedestrian crossings Pedestrians using pedestrian crossings installed close to a roundabout may reduce the vehicular capacity of the junction in two ways. Firstly, for traffic approaching the junction, the combined capacity of the crossing and junction will be lower than either the vehicular capacity of the crossing or the junction capacity considered separately. Secondly, the crossing may restrict traffic leaving the junction, causing blocking back, i.e. traffic queuing in such a way as to block the preceding entry. For standard roundabouts, the two effects are described more fully in SR 724 (Marlow and Maycock, 1982). The Zebra crossing model within ARCADY is based on the effects described in that report, while the Pelican crossing model is based on the effects described in Griffiths J D, 1979.

An enhanced Pelican Crossing model means that ARCADY can now model the capacity and delay effects of signal-controlled crossings at standard roundabouts.

The pedestrian flows at a crossing can be specified in one of three ways:

i) as direct data, in which case the flow per minute is input for each time segment. ii) as a constant flow throughout the modelled period, in which case the flow per

hour is input. iii) so that the shape of the pedestrian flow profile is the same as the vehicular

demand profile for the same arm. In this case the average pedestrian flow per hour is input.

In the second and third cases the pedestrian flows are determined for each time segment within the program. ARCADY models the effect of Pelican and Zebra crossings differently. The same models are used for both standard and mini-roundabouts. Sections 4.5.1 and 4.5.2 explain the two different approaches. 4.5.1 Zebra crossing model

For a Zebra crossing a theoretically-based model is used as follows: The length of the crossing is used to calculate the time taken for a pedestrian to cross at an assumed speed of 1.4 metres/second. Where a crossing has a central refuge the length of each section is treated separately. For each time segment the vehicular

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capacity of the crossing is calculated using a modified form of equation (3) of SR 724 (Marlow and Maycock, 1982). Two situations can occur (section 4 of SR 724):

i) the crossing capacity is less than or equal to the entry capacity - in this case, the crossing dominates the junction entry and the capacity is restricted to that of the crossing

ii) the crossing capacity is greater than the entry capacity - the capacity of the

combined system is then calculated using the methods described in SR 724. For traffic leaving the junction the queue-length probabilities at the crossing are determined from the ratio of traffic flow to the crossing capacity, and from the ratio of time for a pedestrian to cross to the mean time headway between vehicles. The proportion of the time when a queue stretches back from the crossing to the previous entry is calculated, according to SR 724 (Table 1), and the junction entry capacity for that arm is reduced by the same proportion. Delays to the exiting traffic itself are not calculated. 4.5.2 Pelican Crossing model

For a Pelican crossing a theoretically-based model is used as follows: 1. The user specifies pedestrian flow data and a comprehensive set of crossing characteristics. These details are then used to calculate the average green and red time for the Pelican crossing using the method suggested in “Mathematical Models for Delays at Pedestrian Crossings” (Griffiths, 1979). 2. A reduction in capacity is calculated iteratively using a procedure which takes account of the capacity of the approach without the presence of the crossing and, the size of the reservoir of traffic (in vehicles) which can queue between the crossing and the junction.

The model in ARCADY 5 which allowed the effects of either Zebra and Pelican on capacity to be estimated for mini-roundabouts has been replaced with a more detailed Pelican Crossing model. The Zebra crossing model (previously only applied to standard roundabouts) is now used for both mini-roundabouts and standard roundabouts.

4.6 Site-specific capacity corrections The major source of error in queue-length and delay estimates comes from inaccuracies in the calculation of capacity. Implicit in the capacity formulae is an error due to


unexplained site-to-site variation, and this can be removed for existing junctions by making on-site observations of the entry capacities. The capacity formulae incorporating a correction calculated in a previous run will also be appropriate in cases when small modifications to the junction are being assessed. The methods of collecting local data and the corrections to the capacity formulae are fully described in Appendix D (page 227), and in LR 942 (Kimber, 1980). This procedure produces a correction (of intercept) to the capacity relationship of the arm(s) in question, and the queue/delay calculations will consequently be improved. Site-specific corrections may be applied to any arm of a junction, and are in the form of a correction to the intercept of the entry capacity equation (Fi of equation (1) in Section 3.4, page 12). Observations of circulating flows and entry capacities are made when there is continuous queuing at the junction entry. The collected data is used within the program to calculate the correction to the intercept.

Site-specific correction can also be applied to mini-roundabouts. The mini-roundabout capacity formulae are similarly adjusted by a calculated intercept correction value.

An intercept correction calculated during a previous run may still be appropriate in a new design, where minor changes are made at one or more junction entries, but only when these are made to the geometric parameters used in the capacity calculations (An example of a minor change is the movement of a kerbline to increase entry width).

The use of previously calculated intercept corrections is not appropriate if changes are made which are not related to parameters used in the capacity calculations. Examples of such changes include: altering the island size, changes in signing, re-marking of the junction or complete resurfacing. These features may result in a change of capacity, which would not be taken into account in the ARCADY model. If such features are changed, and the user wishes to apply a capacity correction at the site, it would be necessary to take the traffic measurements after the changes have been carried out.

4.7 Grade-separated or very large junctions A roundabout is defined as grade-separated in ARCADY if it connects with a dual carriageway or motorway passing under or over it, or if it connects directly with a motorway. In addition, a roundabout should be modelled as “grade-separated” if it is very large - that is, with a maximum overall diameter in excess of 130 metres. The treatment of grade-separated roundabouts in ARCADY incorporates the research conducted into the operation of many more grade-separated roundabouts (Marie Semmens, 1988) in addition to those covered in an earlier study (Marie Semmens, 1982). As a result of this work, in ARCADY 6 ALL arms of a grade-separated

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roundabout have a different capacity relationship from that applied to arms of a “normal” (non grade-separated) roundabout. The capacity relationship used for all arms of a grade-separated roundabout is:

Q (entry capacity ) = 1.004F - 0.036SEP - 0.232Q + 14.35

- f Q (2.14 - 0.023Q ) pcu / min.

e c

c c c

where

F and fC are the normal intercept and slope of the capacity equation (i.e. without the grade-separated effect) expressed in pcu/min. __ QC is the mean circulating flow past the arm under consideration for the central 30 minutes of the total modelled period, expressed in pcu/min.

__ QC. represents a mean ‘historic’ value for the circulating flow while Qc is an ‘immediate’ value of the circulating flow – the two values should not be confused with each other.

SEP is relevant only for arms consisting of separate entry and exit slip roads. It is the separation between the point where the arm enters the roundabout and the point at which the same arm leaves the roundabout. It is important to note that arms of this type should be treated as a single arm, not as separate entry-only and exit-only arms (Section 9.3, page 179). For the other arms, no value is entered and SEP becomes equal to zero in the above equation.

The detailed measurement of SEP is described in Appendix B, page 215. Thus, in general, the entry capacity in the absence of circulating traffic is larger, but the entry capacity decreases more rapidly as circulating traffic increases, compared with at-grade roundabouts. In general, grade separated roundabouts have a larger intercept, but a steeper slope, in their capacity relationships. 4.8 Marginal effects analysis In ARCADY there is an option to predict the marginal effects on capacity and accident rates of small discrete changes in junction geometry and also, in the case of accident analysis, of changes in flows. This may be useful by indicating to the user which parameters to change to achieve, say, a required increase in capacity, or reduction in accident rate, on a particular arm. The program will output the marginal effects analysis for each time segment, and for each arm, as follows:


4.8.1 Standard roundabout model

Capacity effects: The predicted effect on capacity of: an increase in entry width of 0.1 metres an increase in flare length of 1.0 metres an increase in inscribed circle diameter of 1.0 metres an increase in entry angle of 10 degrees

Accident effects: The predicted effect on vehicular accident freq./index of: an increase in entry flow of 1000 vehs. / 24 hours an increase in circulating flow of 1000 vehs. / 24 hours an increase in island diameter of 1.0 metres an increase in entry path curvature of 0.01m-1 an increase in approach curvature of 0.001m-1

and… The predicted effect on pedestrian accident freq./index of: an increase in pedestrian flow of 1000 peds. / 24 hours an increase in entry flow of 1000 vehs. / 24 hours an increase in circulating flow of 1000 vehs. / 24 hours

The program uses calculus to derive these effects; that is, by differentiating the capacity equation with respect to the variable being considered, at the current operating point. It should be borne in mind, however, that this implies measuring, at the operating point only, the slope of a relationship which is generally non-linear. It follows that the effect of large increases in the parameters listed above cannot be determined accurately by simple multiplication. 4.8.2 Mini-roundabout model

The mini-roundabout model uses a re-calculation technique rather than the calculus solution used for standard roundabouts. The recalculations are carried out on values which are scaled by +10%. The predicted effects of the following values are calculated: Capacity effects:

entry width minimum approach half-width

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effective flare length entry corner kerb length distance between arms

Accident effects (Full Accident Model Only):

left turn flow* ahead flow (4-arm only)* right turn flow* sight distance to right from 4m (4-arm only)* sight distance to right from 50m* Min. distance from junction centre to projected arm centre line (4-arm only)* angle between arms* pedestrian flow entry corner kerb line length of island (3-arm only) entry width along give-way (3-arm only) number of entry lanes (3-arm only) junction centre to kerb distance (4-arm only) effective flare length (4-arm only) entry path curvature presence (4-arm only)

* Changes to these variables may affect the number of accidents predicted on more than one arm, hence they are displayed in a separate table in the output file which is easier for the user to understand

4.9 Demand flow options The user can select one of five options. These options are named DIRECT, LEVELS, FOUR, ODTAB, and SATURATION. The DIRECT form of demand flow data input is the most accurate method of specifying the flow/time profile. However, if such information is not available, the user selects one of the three options (LEVELS, FOUR or ODTAB) in which the program calculates, using coarser data, the flows for each time segment. The SATURATION option is described in section 4.9.5, page 33. 4.9.1 Demand flow profile data entered directly - DIRECT

Detailed demand flow profiles (i.e. mean traffic flow in each time segment) can be directly input to the program.


4.9.2 Profile synthesised from time/flow data - LEVELS

Figure 4-1 shows the “theoretical” shape of a synthesised profile in which each part of the central (peak) region forms part of a Normal curve. Figure 4-2 shows the actual histogram produced when the time period is divided into time segments (8 in this case, although it could be any number). These diagrams show the required input parameters: q1 is the pre-peak flow, t1 the time of onset of the peak, q2 the flow at the height of the peak, t2 the time that this occurs, q3 the post-peak flow and t3 the end of the peak. These may differ from arm to arm. t4 is the total duration of modelling and is the same for each arm. The exponential term (“shaping term”) in the equation of a Normal curve is used to obtain appropriate values of q between the fixed points t1 and t2 and between the fixed points t2 and t3. The qi (i = 1 to 3) values act as scaling factors.

Demand flow

q2

q3

q1

t1 t2 t3 timet4

Figure 4-1 Theoretical shape of profile synthesised from data (‘LEVELS’)

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q1

t1 t2 t3 time

q3

q2

t4

Figure 4-2 Actual segment flows used by ARCADY (‘LEVELS’)

4.9.3 Profile synthesised from four hourly flows - FOUR

Traffic demand data is often available as counts for a series of consecutive one-hour periods. Such data is very coarse and gives little information about the detailed shape of the underlying demand profile (the method is, however, more accurate than ODTAB, providing turning proportions are also available). A method for estimating this profile and its associated parameters from four consecutive hourly flows has been developed, and is described in SR765 (Burrow, Kimber, Hoffman and Wills, 1983).

Again the profile is assumed to be a Normal curve, as illustrated in Figure 4-4. The parameters defining it are similar to those required as input to the LEVELS option (see Figure 4-3). They are:

B = the base (or minimum) flow level S = the scale factor: the difference between the maximum and minimum

flow values p = the peak time d = the half-duration of the peak


If

( )

2d

pt

x

2

⎥⎦⎤

⎢⎣⎡ −

−= ...…………..............................................(1)

then the traffic demand, q , at a particular time t is given by:

q = B + S eX ...........................…..............................…….…. (2)

From the four hourly counts the program calculates these values, and hence the demand flow in each time segment, as in Figure 4-4.

Examples of suitable periods to be modelled by the method are 0600-1000, 1500-1900, or 1600-2000. The use of this option is recommended only in cases where the flows for the four hours (q1, q2, q3 and q4) are such that q2>q1 and q3>q4. If this is not the case, the method cannot accurately reflect the underlying profile. Whenever q2 and q3 are approximately equal the accuracy of the method may be improved by moving the modelled period backwards or forwards by half an hour if the required data is available. It should be noted that in certain cases the program uses a slightly modified form of equation (2) to give more emphasis to accurately predicting the flows in the central portion of the four-hour period, rather than the “off-peak” periods. The modelled period can be split into any integer number of time segments (10 in the example shown in Figure 4-5).

Figure 4-3 Parameters of the normal curve (‘LEVELS’ and ‘FOUR’)

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demand flow

1st hour 2nd hour 3rd hour 4th hour time

q4

q3

q2

q1

Figure 4-4 Theoretical shape of profile synthesised from data (‘FOUR’)


1st hour 2nd hour 3rd hour 4th hour

demand flow

time

Figure 4-5 Actual segment flows used by ARCADY (‘FOUR’)

4.9.4 Profile synthesised from origin-destination table - ODTAB

It will often be the case for new schemes that the only flow information available will be in the form of daily turning volumes produced by a traffic model. The Traffic Appraisal Manual (DMRB 12.1) contains advice on the estimation of peak hour turning volumes from such data, and how the estimates should be treated to take account of uncertainties inherent in them.

Given peak hour flows in the form of an origin-destination table, the program constructs peak synthesised demand profiles for each arm by estimating the flow parameters (Figure 4-6) which are used in Section 4.9.2, page 27 (Option LEVELS).

The following algorithm is used:

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i) Suppose the total demand on an arm during the peak hour is Q vehicles/hour.

ii) Set 60Q 0.75 =q =q 3 1

and 60Q 1.125 =1.5q =q 1 2

with t1 = 15 minutes ) This is equivalent t2 = 45 minutes ) to a peak of one hour t3 = 75 minutes ) with 15 minutes each of t4 = 90 minutes ) pre-peak and post-peak

Where q1, q2 and q3 are in vehicles/minute. Then the total flow during the peak hour is a good approximation to Q vehicles/hour. Figure 4-7 shows the actual histogram produced when the time period is divided into segments (6 in this case, although it could be any number).

Figure 4-6 Theoretical shape of profile synthesised from data (‘ODTAB’)


demand flow

t1 t2 t3 time

Figure 4-7 Actual segment flows used by ARCADY (‘ODTAB’)

4.9.5 Fully saturated mode - SATURATION

The program can be used in a different mode, simply as a calculator of the traffic capacity on all arms and hence the full capacity of the roundabout. This is called the “fully saturated” option. To model “fully saturated” conditions the program assumes a demand flow on each arm of 10,000 vehicles per minute. The capacities output can be considered to be the maximum demand flow which can be catered for by each arm, for the given turning proportions. However, the user should note that because of the interaction between entry and circulating flows the entry capacities would change if the turning proportions changed. These capacities should not therefore be regarded as the absolute maximum inflow that can be achieved on each arm.

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4.10 Turning proportions The measurement of turning proportions can be treated as a separate exercise from the measurement of demand flows (unless ODTAB is specified). However, they should ideally be measured at about the same time. Turning proportions may be specified in one of three ways:

i) they may be input directly to the program, either for each time segment or for the period as a whole.

ii) they may be estimated within the program from junction entry and exit counts

using a Furness type iteration procedure. iii) if no turning count information is available, the program applies default values.

The values are listed in Table 4-1

TABLE 4-1 DEFAULT TURNING PROPORTIONS

Proportion of Traffic to: No. of Arms 1st Arm 2nd Arm 3rd Arm 4th Arm 5th Arm 6th Arm

3 0.5 0.5 4 0.185 0.63 0.185 4 MAJOR 0.125 0.75 0.125 4 MINOR 0.22 0.56 0.22 5 0.125 0.375 0.375 0.125 6 0.1 0.25 0.3 0.25 0.1 7 0.1 0.15 0.25 0.25 0.15 0.1

In (ii) entry (demand) and exit flows are both input to the program using the same input option. The total exit flow is calculated and scaled to equal the total entry flow. The turning proportions are calculated for the whole modelled period or, if required, for each time segment. In the case of a 4-arm roundabout the default values used depend on the relative importance of the arms. When the roundabout approaches are clearly distinguishable in importance, i.e. a major road (often a dual carriageway) is crossed by a minor road, the general default values for 4-arm roundabouts are replaced by the default values for 4-arm major entries and minor entries - see above. A 4-arm junction of this type is identified by the approach road widths of their respective arms.


It must be emphasised that the default turning proportions, being “global” values, are not likely to give very accurate results and should only be used as a last resort. Cases where the default values are likely to be significantly inaccurate include:

i) Junctions that do not have four arms. Since these only have single sets of default values it should be recognised that they can only be approximate and do not take account of major and minor entries.

ii) Junctions with entry-only or exit-only arms. iii) Grade-separated roundabouts, where there would be virtually no traffic going

straight on from an exit slip road to an entry slip road of the same motorway/dual carriageway.

It must also be recognised that the default values do not make any provision for U-turning traffic, or variation by time segment or arm. 4.11 Heavy vehicle percentages A heavy vehicle is defined in ARCADY as a vehicle with more than four tyres in contact with the road, including any trailer. Heavy vehicle percentages may be specified in one of two ways:

i) they may be input directly to the program, either for each time segment or for the whole modelled period, or

ii) if no information is available, the program can apply a default value of 10%

heavy vehicles, which applies to all arms and all time segments. 4.12 The effects of lighting and surface conditions When modelling a standard roundabout the user has the option of specifying conditions of daylight or darkness when carrying out a run of the program. Research by Burrow (1986) indicates that junction capacities are reduced by five percent in dark conditions. This option is intended for modelling conditions at night. No distinction is made about the level of road lighting present. All of the roundabouts studied by Burrow had “adequate” road lighting; normally this will be the case for any roundabout modelled. Surface conditions are not modelled for standard roundabouts. When modelling a mini-roundabout the user has the option of specifying ‘normal’ conditions, daylight or darkness. Research into mini-roundabouts indicates that mini-roundabout capacities are reduced in dark conditions. The same research into mini-roundabouts also indicates that mini-roundabout capacities are also reduced in wet

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conditions, therefore the user also has the option of specifying road surface conditions as normal, dry or wet. If the user does not wish to model different lighting conditions the ‘Normal’ option should be chosen. The program will assume ‘average’ lighting conditions. Similarly, if the user does not want to model wet/dry conditions, the program will assume ‘average’ wet/dry conditions when the ‘Normal’ option is chosen. 4.13 Point-to-point journey times ARCADY 6, for the first time, produces point-to-point journey times through the junction. The estimated journey times reported by ARCADY are the sum of the total time that traffic takes to travel from a certain point upstream of the roundabout to a specified point downstream in the absence of any other traffic plus the additional travel time caused by the presence of the traffic (i.e. queueing delay).

The point-to-point values calculated are not simply the geometric delay added to the queueing delays calculated by ARCADY. The reported queueing delay represents only the additional travel time due to the presence of the junction, and excludes the time to travel between the two points if the junction wasn’t there at all.

To obtain the point-to-point journey times, geometric delay data is required and hence the geometric delay option must be selected. An additional table of point-to-point journey times is included with the geometric delay results. The average journey times (over the whole modelled period) from the every origin to every destination is tabulated. The journey time calculation begins the user-specified distance upstream of the give-way line and ends the same distance downstream of the junction exit, i.e. it includes the time taken to travel along the approach to the roundabout, round the circulating carriageway to the exit arm, and then along the exit arm, together with any queuing delay at the roundabout entry. The upstream/downstream distance is measured from the give-way line. The distance upstream/ downstream on each approach/exit is set by the user, e.g. if the value set on Arm A is 200m, then this distance defines the distance the origin is from the junction for any traffic entering on this arm, and also the distance the destination is away from the junction for any traffic leaving on this arm. To be consistent with the calculation of geometric delay in ARCADY it is assumed that a vehicle approaching the junction will decelerate from it’s cruise speed to a speed determined by the junction geometry and the turning movement being made. Similarly, a vehicle leaving the junction will accelerate from its exit speed until it reaches the desired cruise speed.


The calculated journey time allows for these accelerations and decelerations. If for any arm the distance required for either acceleration or deceleration is greater than the fixed distance referred to above an error is generated and the user should enter a larger distance. 4.13.1 Comparisons with other products

If comparisons between the point-to-point journey times produced by ARCADY and by other software products are to be made, differences in the way the separate programs work should be born in mind. Comparisons between PICADY 5 and ARCADY 6 can be easily made as both programs use the same basic method to calculate the results. If the point-to point delay values are going to be used to compare results from ARCADY and TRANSYT, several differences in the way the two programs work should be borne in mind as follows: Start and End point of Calculation The ARCADY journey time calculation begins and ends a fixed distance upstream and downstream of the junction. To be comparable, the equivalent TRANSYT journey should therefore include a start(upstream) and end(downstream) link in addition to the links comprising the junction. The lengths of these links should be the same as point-to-point delay distances in the corresponding ARCADY file. Choice of Cruise Speeds In ARCADY the user is asked to enter entry and exit link speeds for each arm. The program itself then works out the speed at which vehicles will travel through the junction, and the acceleration/ deceleration required. In TRANSYT the user has to enter the cruise speed on each link. On approach and exit links the speed entered should therefore be an average speed over the whole link allowing for deceleration and acceleration. The speed entered for internal links should also be the average speed at which vehicles are likely to travel whilst on those links.

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Operation of the Analysis Program Page 39

5 Operation of the Analysis Program 5.1 About this chapter If new to ARCADY it is important that all the sections in this chapter should be read. The user that is already familiar with ARCADY 4 or 5 but unfamiliar with ARCADY 6 may skip sections 5.2 - 5.4 entirely or can read through them just as a reminder but should still read section 5.5. 5.2 Queue-length/delay calculations The program operates by first dividing the total time for which capacity and queue-length/delay calculations are needed into a number of smaller, equal time intervals or segments. Then, these segments are considered sequentially. During each time segment, demand flows and capacities are assumed to be constant - time segments are typically 10 or 15 minutes long. In calculating the capacities, queues and delays at a roundabout the program treats the entry arms as a set of inter-connected junctions. The procedure is then as follows:

i) For each entry, the slope and intercept of the entry capacity relationship are calculated from a knowledge of the geometric layout (section 3.4, page 12), taking account of whether or not the roundabout is grade-separated. The intercept may be modified if site specific data is input (section 4.6, page 22).

ii) The profile of demand flows over time is calculated where appropriate, and

values derived for each time segment. iii) For each time segment the entry flow, circulating flow, entry capacity and final

queue-length are calculated for each arm, taking account of the flows from the other arms and of the initial and final queues for the time segment. This involves a two-part iterative procedure.

iv) If required, the geometric delays incurred by traffic during the period are

calculated. This only applies to standard roundabouts – they are not calculated for mini-roundabouts.

v) The final queue-lengths of one time segment are taken as the initial queue-lengths

for the next segment. vi) The procedure is repeated segment after segment until the whole of the modelled

period (usually a traffic peak with some off-peak either side) has been processed.

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5.3 The procedure in detail The program reads the “parameters” and “principal options” data which determine the particular user requirements for the run. Geometric parameters for each arm of the roundabout and traffic flows (which is the minimum amount of data required for a run) are then read. Depending on the user’s specified requirements additional data may also be read, for calculating geometric delays, accident predictions, etc. All data input to the program is output for verification and future reference. The geometric parameters are used to calculate, for each arm, the constants Fi and fi of the entry capacity relationships. For an at-grade junction these values are used directly by the program. If a roundabout is grade-separated the capacity equations for all arms are modified (section 4.7, page 23). When local data is available a correction may be made to Fi (section 4.6, page 22). Such a correction is either calculated from observed entry capacities and circulating flows, or is input directly as a correction to the intercept (which has been calculated from a previous run of ARCADY). When details of geometric delays are required, the approach and departure speeds and geometric parameters are used to calculate the geometric delay associated with each traffic movement. The calculation of these delays is described in section 4.3, page 18. The program then determines the demand flows (in vehicles per minute) for each stream for each time segment. Either these have been read in directly or they are calculated from other input data. If turning proportions are to be estimated from entry demand flows and exit count data, then the exit flows are determined for each arm and for each segment by factoring the exit counts, such that the total entry flow into the junction matches the total exit flow from the junction. A Furness balancing procedure is then used to estimate the turning proportions. The percentages of heavy vehicles and traffic turning proportions are given default values if required, and are printed for verification. If any zebra or pelican crossings are included, the geometric parameters associated with each crossing are printed. The pedestrian flows (per minute) are read in directly or are determined (Profile or Constant Demand) for each crossing for each time segment. The queue-lengths at the start of the first time segment are assumed to be zero. The entry flow for each arm is calculated, using the demand flow, the slope and intercept values and the circulating flow past the entry. The queue-lengths at the end of the first time segment and the delays incurred during the segment are then calculated for each arm, using the entry capacities and demand flows.


If requested, the geometric delay is calculated by aggregating the delay calculated for each vehicle arriving on the arm for each time segment. At the end of each time segment the following values appropriate to that segment are output for each entry arm:

demand flow, capacity, traffic intensity (ratio of flow to capacity, or RFC), initial and final queue-lengths and delay.

Additional data may also be output, depending on the various user options selected. The program then repeats the whole procedure for each time segment. The final queue-length for one time segment is taken as the initial queue-length for the following segment. When the processing of all time segments has been completed, the queuing delays previously calculated for each time segment are summed over the whole period for each arm, and for all arms together. Two measures of overall queuing delay are given:

i) total queuing delay (veh-min) experienced by vehicles within the time period being modelled, and

ii) “inclusive queuing delay” which is the total delay plus any extra queuing delay

incurred by vehicles which have arrived during the time period but which are still queuing at the end of it.

If there are no queues left at the end of the program run, the two measures of total queuing delay are identical. Total demand flows and delays per vehicle are also calculated. If geometric delays are being calculated, these are aggregated and output in a second summary table. If, at any time during a run, flows are such that the capacity of any stream becomes zero, the program continues to run but a warning message is printed out. Warning messages are also printed if pedestrian flows seriously reduce the junction entry capacities, or are likely to cause the junction to completely lock up. The calculations required for accident prediction take place entirely separately from the above procedure for capacity, queue and delay calculations and the results are printed separately. Calculations related to queue-length distributions (i.e. day-to-day variability of queue lengths) are also carried out separately; in this case they are performed during a second pass of the program, making use of knowledge of the build-up and decay of queues output from the first pass. This two-pass process is automatically carried out and is hidden from the user.

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The GUI makes use of the entry capacities, that are calculated for each time segment, to calculate the average delay for a vehicle arriving on each entry arm during each of the time segments . The results are added to the existing output file next to the other segment results.

5.4 Numerical accuracy The accuracy of the results from the program will reflect the accuracy of the input. For example, if data is input at the coarsest level, using all the default options available, it is unlikely that the results will accurately reflect operation at a particular site. Default values should therefore be used with care, only when it is impractical to obtain better data. Whenever defaults are used it will frequently be necessary to justify their use to other interested parties.

ODTAB should only be used to specify demand flows when it is not possible to use one of the more accurate methods. It can, however, be used to determine turning proportions in conjunction with some other method of specifying demand flows.

At a typical site, the standard error of the capacity prediction for a standard roundabout, at the mean point, is 15 percent. This standard error takes account of both the random variability between supposedly identical sites, and the random variability that may occur at a single site at different times of day. At mini-roundabout sites the unexplained variance in capacity (outside the model) is less than 40%, a value 38% smaller than if the standard roundabout model was used to model a mini-roundabout. For a given capacity the queue-length and delay predictions are the average values of broad distributions, and there will be considerable fluctuations in the values observed at the same time on different days (Section 4.2, page 17). Small numbers of individual observations of these quantities are unlikely to be sufficient to provide reasonable approximations to the average values predicted by the program. The standard error of the prediction of the average depends on a range of circumstances and it is not possible to give a single representative value. All details of the various factors involved in capacity prediction are contained in SR 582 (Kimber and Coombe, 1980). As mentioned above, individual capacity predictions are subject to statistical error. If the capacity is accurately predicted, then the queue-length and delay predictions will correspond to the average values of correct distributions. However, in a minority of cases the capacity characteristics of individual sites may differ appreciably from the average, and queue-length and delay estimates will consequently


be affected. Thus, if the capacity is less than average the queues and delays will be underestimated and if it is greater than average they will be overestimated. The accuracy of the capacity and delay calculations for an existing junction may be improved by use of local traffic observations to modify the entry capacity equations of one or more streams (section 4.6, page 22). The traffic observations are made when the particular stream is operating at capacity, and the resulting correction to the capacity equation may also remain applicable after minor junction modification schemes. The technique improves the accuracy of modelling by eliminating the variation between sites implicit in the capacity equations. Use of the “Marginal Analysis” option (section 4.8, page 24) will be of value to the user who is concerned with the robustness of a particular design. Use of the program should in general be limited to situations in which the values of the parameters involved lie within the range of values over which the relationships used have been calibrated. However, in situations where conditions may be modelled, but are such that there is some doubt over the accuracy of the results, warning messages are given which are explained in Section 8.6, page 173. 5.5 Files associated with ARCADY 6 ARCADY has several files associated with the graphical interface (GUI) and the analysis program. These files are: An input data file (.VAI) - This file stores the data entered by the user, for subsequent editing or running. The file can be given any suitable filename by the user, and it will be given a default “.VAI” suffix by the program (no other extension is allowed). An analysis output or “ASCII print” file (.VAO) - Created by the analysis program, this file contains the ‘standard’ program output for subsequent printing. Again, it may be given any suitable filename by the user – in this case, the program will add a “.VAO” suffix (again, no other extension is permissible). A report or “graphical” file (.VAR file) – Created by the report designer, this file contains the user-defined report featuring analysis output tables and graphs in a graphical screen (i.e. not ASCII). The report is written to a file with the same name as the standard “ASCII print” file, but with a “.VAR ” suffix.

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An HTML report (.HTM) – Created by the report designer, this file contains the same report as the ‘VAR’ file, but in a more universally accepted format, i.e. HTML. Again, the report is written to a file with the same name as the standard “ASCII print” file, but with an “.HTM” suffix. A bitmap file ([filename]_XXCADYReportImageN.BMP) – Created by the report designer, these files contain the graphics referenced by the HTML (.HTM) report. The files are prefixed with the results file filename and end with the number of the graphic within the report, e.g. the second image in the report for the data file SAMPLE1.VPI will be “SAMPLE1_XXCADYReportImage2.BMP”. A junction image file (.VAJ) – An ARCADY 6 data file can make reference to any image file chosen by the user. Subsequently, it can be added to the user-defined report. The file referenced is stored as a “.VAJ” file. Several image formats are acceptable, e.g. BMP, JPG, GIF, WMF, EMF, etc. DWG is not currently supported. A report template file (.TEM) – This is a text file that contains a definition of a graphical report defined by the report designer. It may be given any suitable filename by the user - the program will add a “.TEM” suffix (again, no other extension is permissible). A report template graphics file (.TEX) – This is a file used by the report template to store the graphics associated with the format of the report itself, e.g. the header and footer graphics (which will be chosen invariably to include a company logo).

A true-type fonts file – XXCADY.TTF This is a font file containing arrow characters used in the junction diagram and in the turning proportions tables, etc.

Matrix File ACMAT.DAT This file is used to store data essential to the calculation of accident predictions.

5.6 Queue variability There is an option to produce predictions of the variability of queues (i.e. from day to day - section 4.2, page 17). This feature involves two runs of the analysis program. During the first run the analysis program adds extra data to the input data file (i.e. card type 31). During the second run this data is used by the program to produce the final queue variation results. This process is transparent to the user, i.e. once queue variability is specified by the user the program automatically carries out both runs of the program,


deletes any temporary files, and produces the information on queue variations. Therefore, for anyone auditing ARCADY data files, there is no need to examine Card 31 as it is generated by the program itself – not by the user. 5.7 Site-specific data (observed flows / intercept correction) If site-specific data (observed flow data) is specified when an analysis run is requested ARCADY calculates a set of (site-specific) intercept corrections and writes these to the data file which the GUI automatically reads back into memory. The program then automatically performs a second run using these intercept corrections to determine the capacities, queue lengths, etc. In the amended data file the site-specific flow data option is de-selected and the site-specific intercept correction selected instead, so that any subsequent runs will automatically use the new intercept correction factors.

ARCADY no longer asks the user to save the data to a new file as ARCADY 6 retains the site-specific flow data in the existing file even after the site-specific corrections have been calculated.

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Graphical User Interface (GUI) Operation Page 47

6 Graphical User Interface (GUI) Operation 6.1 About this chapter This chapter describes all the features associated with ARCADY’s graphical interface. If you are familiar with ARCADY 4 or ARCADY 5 it is important to read sections 6.3, 6.10 – 6.14 and 6.18 of this chapter as these describe new or revised features. Everyone else should read ALL of this chapter. Detailed descriptions are given of each feature with accompanying figures when they are appropriate. Although the general functionality of the junction data-entry windows are amongst the features described in this chapter, details of the data input process are in chapter 7. 6.2 Main menu system All the main features of the program are accessed through a menu system. This consists of a “main menu” made up of several pull-down menus and also a toolbar (see Figure 6-1). A checklist assists the user in keeping track of the data-entry process (section 6.4, page 50). The main menu has the following headings: FILE, VIEW, DATA, RUN, OPTIONS, WINDOW and HELP. Each of these menu headers consist of several options that are described in detail in sections 6.4 to 6.13.

Figure 6-1 Main Menu To summarise their function: i) FILE is used to load, save and print files. ii) VIEW allows input and output files to be viewed. iii) DATA allows access to the data-entry windows.

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iv) RUN is used to execute the analysis program, run a graphical report, open the

report designer and open the graph designer. v) OPTIONS allows the user to specify ARCADY’s various configuration “user”

settings. vi) WINDOW provides access to each of the current windows used by the GUI

(e.g. graphs, tables the checklist). vii) HELP provides access to all the Help files supplied with the program.

6.3 Main Toolbar The most commonly used features of the program are accessed through the main toolbar. The following table describes the basic function of the status bar, which is located at the bottom of the screen, and the toolbar buttons. The sections which describe their function in more detail are also referenced. Toolbar Button

Function More detail

Allows junction data to be reset, loaded and saved.

Section 6.8 page 53

Runs ARCADY model

Section 6.6 page 52

Launches the VIEWER program which displays the ‘standard’ ASCII output results

Section 6.15 page 78


Reveals a diagram of the complete junction with basic geometric features displayed. These features are updated whenever a new file is loaded or when geometric data is changed. The diagram can also be used to display queue animations.

Section 6.10, page 57

Launches the Graph Designer Section 6.14, page 75

Launches the Report Designer Section 6.12, page 61

Runs ARCADY model AND the report Section 6.12, page 61

Displays the report created by the Report Designer. The report can be printed from here.

Section 6.13, page 71

Launches the Help Tips File and displays context-sensitive help when it is appropriate.

Section 6.19.2, page 90

Loads the main Help file. Section 6.19, page 89

6.3.1 Status bar

The status bar (located at the bottom of the screen) displays the title of the currently selected data-entry window. In addition to this, it displays a variety of messages designed to inform the user of what task the program is currently doing or has recently completed and also displays the status of some aspects of the software, e.g. the ‘driving side’ is shown as well as the ‘units of measurement’.

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6.4 Keeping track of data-entry A checklist allows the user to keep track of the data-entry, and is central to the data-entry process (see figure 6-2).

Figure 6-2 Progress Checklist The checklist consists of a vertical column of buttons which allow access to each of the data-entry windows. The checklist only allows entry to those windows that have had certain pre-conditions met. Therefore, most buttons will only be enabled once earlier windows have been completed. For example, the principal options cannot be entered until such time as the junction type has been entered. A green coloured tick (see figure 6-2) will appear beside a data-entry button once data has been entered for that window. The green tick does not indicate that all of the required data for that window has been entered. An arrow will appear next to the currently selected window. The checklist can be shown in its ‘original’ vertical orientation or in a new horizontal orientation, selected from the main menu using Data/Checklist. ARCADY 6 also remembers the location of the checklist from the last time ARCADY was run. The


checklist can also be displayed permanently using one of the user options (see section 6.18, page 83) 6.5 Data-entry windows functionality A series of windows (and frames within them) allow the user to enter the necessary information about the junction and the current run of the program. Variations of the presented windows and associated frames may occur, depending on the user’s responses within previous windows. In addition, the selection of certain choices may have already been made by the program, or they may be disabled as they appear on the screen. This occurs when options become logically incompatible with the user’s choices made in earlier windows. After completing a window the user can either confirm that all the information is correct by pressing <OK> or to ignore all the changes carried out within the window by pressing <Cancel>. If there are any particular consequences of having changed some data in the window a warning message will appear asking the user to confirm the saving of this data. If any of the values within the current frame of the window are invalid when the user presses <OK> the program will carry out its usual data error handling sequence as explained in section 7.2.3, page 94. In most cases, users are prevented from entering data which falls outside the acceptable range. Further details, describing the operation and data requirements of each of the windows, are given in “Data Input” (section 7, page 93). 6.5.1 Graphical assistance

In several of the data-entry forms there is either an aerial view of one of the arms of a roundabout plus part of the roundabout itself or a view of the whole roundabout. Line drawings (in yellow) are superimposed onto this schematic diagram to show details of what data values are required. The drawings come into view as each control gains the focus (see figure 6-3).

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Figure 6-3 Graphical assistance

When the drawings show a particular feature they are not intended to indicate the existence or absence of that feature (pedestrian crossings are one exception to this rule).

6.6 Running the analysis program The analysis program can be run directly from the GUI or run via a new ARCADY 6 feature called the “Report Designer”. The Report Designer is described in section 6.12, page 61). The analysis program can be run directly by clicking on the RUN button on the toolbar or by selecting it from Main Menu/Run. When run, the program does three things. Firstly, it makes a backup of the currently selected input file calling it “ARCADY6.BAK”. (in case the user accidentally overwrites it) Secondly, it saves the currently loaded data to the selected input data file (“.VAI” file) and thirdly, it runs the analysis program which uses the input file data to carry out its calculations. The resulting ‘standard’ analysis output is saved to a separate ASCII file (“.VAO” file) specified by the user. This file can be viewed using the VIEWER program (section 6.15, page 78).

If any of the required data is missing or incomplete the analysis program may not carry out any calculations. If this happens either the GUI or the analysis program will produce one or more error messages.


6.7 Batch processing of data files Multiple files may be selected and run consecutively in a ‘batch mode’ in ARCADY. Main Menu/Run/Run Batch brings up a window in which you can chose multiple files for analysis (standard windows multi-selection method is used) and run by pressing the <Run Data> button (See figure 6-4). Another window displays a report on the outcome of each run as it is carried out. Each data filename is shown with any warning or error messages displayed below it. The number of successful runs and total number of runs attempted are shown at the end of the batch run report.

Figure 6-4 Batch processing 6.8 Saving and retrieving input data files The saving and retrieving of input data files within ARCADY is simple, convenient and, above all, versatile. Users can decide themselves how to manage their files. A single window allows the user to change drives, directories and browse through collections of files. The run title and last-modified date of each valid ARCADY file is displayed when it is selected. Details on saving and retrieving files are described in sections 6.8.1, page 54 and 6.8.2, page 55.

The default windows used for file selection (e.g. LOAD DATA and SAVE DATA) do not always allow access to all valid drive names when used in conjunction with network drives. A ‘standard’ window can be used instead of the default, which is set using a User Option’ (see

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section 6.18.7, page 85). The standard file selection window allows access to any available drive. Unfortunately, this window will not display the run title or last-modified date of the selected file, so you may wish to continue to use the default selection method unless you have problems accessing certain network drives.

6.8.1 Saving input data files

Input data files can be saved at virtually any time by accessing either the Save button on the toolbar or via the File/Save and Save As... options. Save As... allows the user to specify a new filename or select an existing filename to which to save the data. A window similar to that shown below (see figure 6-5) is used to specify filenames.

Figure 6-5 Save File As… Firstly, the user should select the required disk drive and subdirectory. The current filename will either be blank or will display the words “< No selected file >” while a filename has not entered or selected. A filename can be selected from filename list-box.

No extension is required - this will be added automatically. Once a filename is entered or selected from the file list-box, pressing the <continue> button will save the current data to the specified file and close the window. If an invalid filename is entered the program will not allow the data to be saved. The same will happen if a file extension other than “.VAI” has been entered - The “.VAI” extension is compulsory for ARCADY input data files.

If the specified file already exists the user will be asked to confirm they wish to overwrite the file.


The <Cancel> button closes the window without saving any data and ignores any changes made whilst the window was open (e.g. a change of subdirectory or filename).

The Save option allows the user to save the current data to the current input filename without having to re-specify the file to be used. 6.8.2 Reading input data files

Input data files can be read by accessing the Open button on the toolbar or via the File/Open File… option. For convenience, a file history list of up to five of the most recently opened input data files is accessible from File/<Filename>. Open allows the user to read previously-saved data into memory (RAM) for editing or in order to carry out an analysis run on it.

Any data currently in memory will be overwritten when using the Open option.

Firstly, the user should select the disk drive and subdirectory in which the required file resides. Before a file has been selected the current filename will either be blank or will display the words “< No selected file >” while a file has not been selected. A filename can be selected from filename list-box (see figure 6-6). Once a filename is selected, pressing the <Continue> button will read the current data into memory. The Run Title box displays the run title of the selected file. See section 6.8.3, page 56 for details concerning older versions of ARCADY files.

Figure 6-6 Read File

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The list-box will, by default, list only “.VAI” files since genuine ARCADY data files must have a “.VAI” extension. For details on reading files created with earlier versions of ARCADY, such as ARCADY/3 files, please refer to section 6.8.3, page 56.

The <Cancel> button closes the file selection window without reading any data and ignores any changes made whilst the window was open (e.g. a change of subdirectory or filename).

If a file is not an ARCADY file the Run Title box will display words to that effect and will not allow the file to be loaded. 6.8.3 Reading older versions of input files

Each ARCADY data file since ARCADY 4, contains the version number of ARCADY that was used to create that file. It is sometimes useful to know that a particular file was created using an earlier version due to format changes and so forth. In order to facilitate the identification of such files the Run Title box which normally displays the Run Title of the selected file, also shows the version number of the file when it does not coincide with the version of ARCADY that is reading it.

e.g. A file created with version 5.00 of ARCADY, containing the Run Title “Example Data 1”, and viewed using version 6.00 (say) of ARCADY will appear as “5.00: Example Data 1”, instead of just the Run Title.

ARCADY/3 data files can be loaded into ARCADY 6. Once loaded, they can be saved in the new ARCADY file format.

To load an ARCADY/3 file the user must first change the file list-box to display files with the old “.DAT” extension and then select the required file. Note that, like the ARCADY 5 files, the file’s Run Title is displayed.

6.8.4 Reading drive-on-the-right and drive-on-the-left input files

ARCADY can model both drive-on-the-right and drive-on-the-left situations. ARCADY will switch automatically to the correct orientation for that file.

6.8.5 Converting ARCADY 6 files back into older ARCADY file formats

ARCADY 6 data files can be converted back into ARCADY 5 files via the main menu option File/Export Input Data as previous version… Data relating to new ARCADY 6 functionality will not be written to the ARCADY 5 formatted file. Appropriate warning messages are displayed when this occurs.


Some examples of data that will not be saved are:

• multiple demand sets (Flow data) • pelican crossing data (Cards 26 and 27) • point-to-point delay measured distance (Card 6). • angles between arms and flow scaling factors (Card 32)

6.9 Specifying output analysis files When an input filename is changed the name of the output file is automatically set to the same name, but with a “.VAO” extension. The user can change this by selecting Main Menu/Run/Change Output File Name. This option loads a file selection window similar to that is used for selecting all file names, but without the Run Title box. If an existing file is selected the user will be asked to confirm that he wishes to overwrite that file with a new output file when it is produced by a run of the analysis program. Changing the output filename may be required for several reasons, such as to avoid overwriting an existing file with the same name or to specify a different directory for the output files. Furthermore, the animation of queue-lengths (section 6.11, page 60) can be carried out solely on the specified file. To carry out the animation on another output file, the new file must be specified as the current output file. Normally ARCADY retains the current input and output directories independently from each other, i.e. if a new data file is read from a different directory the location of the output file generated will not change. Another user option tells ARCADY that it should retain the input and output files within the same directory. (See User options, section 6.18.1, page 83). 6.10 Junction diagram ARCADY has a new facility for drawing a schematic of the current junction based on the available geometric data. The scaled diagram replaces the ARCADY 5 ‘Junction Names’ button on the toolbar and it is also used to display queue-animations (see section 6.11 page 60 for more information on the animation of queues).

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When activated via the main toolbar using the Junction button or by selecting Main Menu/View/Junction Diagram a vector-based scale diagram of the complete junction with the following geometric features is displayed:

• arm names • angles between arms • junction type • actual lane widths • queues (including percentiles) • flare lengths • inscribed circle diameter

Figure 6-7 Junction diagram The screen remains visible until it is closed and is automatically updated to reflect changes to the data set that the user makes, e.g. whenever a new file is loaded or the geometric data changed. The entire diagram automatically resizes if the screen is resized. In addition, options allow the user to adjust the ‘view extent’ of the diagram and whether or not to show certain items. The user options are accessed by using a right-mouse click menu on the diagram.


The three available menu items are: i) Options: Opens the junction schematic user options form. ii) Print: Prints the currently shown diagram. iii) Copy to clipboard: Copies the junction schematic to the clipboard as a

metafile or bitmap so that it can be pasted into another application. 6.10.1 Junction Diagram Options

This window allows the user to change the junction diagram display. The various options are as follows:

Figure 6-8 Junction Diagram Options i) Angle between arms: Allows the angles between each arm to be adjusted to

match the actual junction. This data is not saved however.

i) Zoom To: Zooms the junction diagram to 4 different levels of magnification.

ii) Adjust extent: The window’s ‘field of vision’ or ‘extent’ can be adjusted to show more road space using the extent scroll-bar.

iii) Show Grid: Superimposes a grid over the diagram where 1 square = 1 metre

iv) Queue Animations: See Section 6.11 page 60

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The options chosen are remembered as long as the junction diagram remains open, if you close the junction diagram and then open it again the options are reset. 6.11 Animation of queues ARCADY can highlight the interaction occurring between arms of a junction by showing the queues on the Junction Diagram (see section 6.10, page 57). The scroll-bar can be used to display each time segment. An animation effect of the queues over time can also be produced by showing the queues for each time segment one after the other. The rate at which each time segment is shown can be adjusted using the “Animation Speed” scroll-bar This can be set from 1 (slow) to 30 (fast). Pressing the <Animate> button will start the animation, and pressing the <stop> button during the animation will end it. The start time, end time, and interval length are also shown on the junction diagram options form. The mean queues on each arm of the roundabout are displayed for each time segment in the form of coloured bars emanating from each give-way line. The end of each queue is marked with a solid black line so that it is obvious when the queue extends beyond the limit of the window. When this happens, the windows ‘field of vision’ or ‘extent’ can be adjusted to show more road space using the extend scroll-bar. The extent can also be set automatically to a value that will display the full length of the longest queue during the modelled period (so long as this length does not exceed the maximum extent). It is good practice to re-run the analysis program before viewing any queue animations because the data that is used to draw the queues is read from the ASCII output file – Running the file first ensure the correct results are being used. When queue variability is used the percentile queue lengths (5%, 50% (mean), 90% and 95%) will be shown in different colours. The darkest colour represents the 5% mark and the lightest value the 95% mark. The mean value is shown with a black dark border so that it stands out from the other values.


6.12 Running the Report Designer In addition to the ‘standard’ ASCII output produced by the analysis program, ARCADY 6 also has a powerful new facility called the ‘Report Designer’ from which a user-defined report can be ‘designed’. It defines the content of the report to be generated, along with layout and formatting options. The settings may be saved as a report template, so that they can be used again. There is no limit to the number of templates that can be defined. The last used template will be the first loaded; if no templates have been saved the default template is used. The report generated is more graphical in nature compared with the ‘standard’ ASCII output produced by the analysis program itself. As well as all the standard tables of results the report can include diagrams, such as the Junction Diagram, an actual image of the junction, and many graphs.

The existence of the Report Designer does not make the VIEWER program redundant as it is quick, convenient to use, and provides file comparison tools among its many useful features.

The report designer can be opened via the main toolbar using the Report button or by selecting Run/Report Designer. The four toolbar buttons at the top of the report designer are: Toolbar Button Function

New – starts a new template (and clears all current settings)

Open – open an existing template

Save – save the current settings as a template

Default Template – opens the default template

Any template file can be used as the default template simply by renaming it as “default template.tem” and copying it into the application folder, overwriting the existing default template file.

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6.12.1 Items

Figure 6-9 Report Designer - Items To select items to include in the report simply click on them. When selected the item will be highlighted in blue, to de-select the item simply click on it again.

The item icons are:

Table

Diagram

Picture

Graph –plotted using results from the output file

Graph – plotted via the Graph Designer

Annotation

The <Select All> button selects all the items and the <Clear All> button de-selects all the items. (For a full list and description of the items that may appear in the report see section 8 page 143)


6.12.2 Graphs

The graphs screen allows graphs to be specified for inclusion in the report. New graphs may be added, and existing graphs can be modified, deleted and run. To select a graph for inclusion in the report, click on it, a tick will then appear in the box next to it. The list of graphs shows the standard name – it does not show the name as specified by the user. It also shows the x-axis range and whether or not the graph has been modified, i.e. whether it uses standard labelling or user defined ones.

Figure 6-10 Report Designer - Graphs

The 5 buttons below the list of graphs are: Button Function

Add: Opens up the Graph Designer where a new graph may be

specified and added to the graph collection. (See section 6.14 page 75 for more information)

Modify: Opens up the Graph Designer with the currently selected graph to be modified. (See section 6.14 page 75 for more information)

Delete: Removes the selected graph from the collection

Graph options: Opens the graph options screen to allow specification of labels

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and ranges etc (See section 6.14 page 75 for more information)

Run graph now: Runs the graph and displays it in a window

6.12.3 Order

Figure 6-11 Report Designer – Order

The ‘Order’ screen allows the order in which the selected items will appear in the report to be specified. The item order can be rearranged by dragging and dropping. Items may also be disabled for the run by right-clicking on it and re-enabled by left-clicking on it.


Annotations may also be added via this screen by using the 3 buttons: Button Function

Add annotation Opens a popup box in which the annotation text can be written,

when <OK> is clicked the annotation is added below the currently selected item.

Edit annotation Allows the text of the currently selected annotation to be edited.

Remove annotation Deletes the currently selected annotation

The <Reset layout> button resets the layout to match the order in the ‘Items’ screen. 6.12.4 Item Options

There are some additional options associated with some of the items that may be included in the report. These extra options are only available if the relevant item has been selected. The options available for each item are described in the following sections: 6.12.4.1 Item Options: Junction Diagram

Use default settings: The diagram is included in the report using the default setting (i.e. the settings used when the diagram is first opened.) Use settings from current window: The diagram is included using the settings from the currently open Junction Diagram, i.e. extent, queues, grid, etc. as set by the user via the Junction Diagram Options screen (see section 6.10.1 page 59). If no Junction diagram is open this option is not available.

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Figure 6-12 Report Designer – Item Options

6.12.4.2 Item Options: Queue Diagrams:

Every interval: A diagram of queues in each time interval is included in the report. Max queues only: Only one diagram (the interval with the largest queue length) is included in the report.


6.12.4.3 Item Options: Demand Data Graphs:

All arms on one graphs:

Demand Data Graph - All arms plotted on one graph

One graph will be plotted showing all the arms as different colours. (This is not allowed when the ‘Levels’ or ‘Four’ demand data type is used.) A key is provided to indicate which colour corresponds to which arm.

Individual graphs for each arm: A graph for each arm will be plotted. For ‘Levels’ and ‘Four’ demand data this is set automatically, as this is the only option available.

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6.12.4.4 Item Options: Graphs Line Mode:

This applies to all graphs except ‘Levels’ and ‘Four’ Demand data graphs and those generated by the Graph Designer (See Section 6.14 page 75)

Stepped:

Graph plotted using Stepped mode

Plots the graph using the start and end of each interval as the x parameter such that the value (y parameter) is constant throughout the interval.

Continuous:

Graph plotted using Continuous mode (Plots the graph using the middle of the interval as the x parameter.)


Graphs drawn using the Stepped mode (the default) reproduce exactly the output from the ARCADY analysis program. That is, the value plotted is constant throughout each time interval. When using the Continuous mode, the sloped lines produced are interpolations that serve purely as visual aids. (Since it is usually easier to see the trend of changing values when the lines are sloped.) 6.12.5 Formatting Options:

The report options screen allows some formatting of the report.

Figure 6-13 Report Designer – Formatting Options The following formatting options are available: Formatting Option

Options available Applies to

Font Name Arial, Courier New, Times New Roman, Tahoma and Verdana

All text in the report

Font Size Small, Medium or Large

All text in the report

Junction Diagram Small, Medium or Large

Junction Diagram

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Other Diagrams Size Small, Medium or Large Vehicle Prop. Diagrams Turning Prop. Diagrams Queues Diagrams

Graph Size Small, Medium, Large or Extra Large

Graphs plotted using the results from the output file i.e. those in the item list.

User Generated Graph Size

Small, Medium, Large or Extra Large

Graphs created by the Graph Designer (see Section 6.14 page 75)

Units Metres or Decimal Feet All units in tables, graphs and the Junction Diagram

Header and Footer (none) Page n Page n of m Date Filename Run Title Client Job number Picture (Note: click on the picture-preview box to select or re-select a picture)

Three items may be specified i.e. one for the left, one for the centre and one for the right.

Try to avoid using large pictures within headers and footers as they tend to make reports large and are also slow to generate.

6.12.6 Running the Report

Once the report settings have been set, the report can be generated by clicking on the Run Report button. This runs the analysis program, creates the report, and opens up the report viewer with the generated report showing. The report is automatically saved in two different formats (.VAR and .HTM)


6.13 Report Viewer There are several ways to launch the Report Viewer: Run a report

Opens the generated report in the report viewer

Preview Opens the report viewer with the current report showing or a blank screen if there is no existing report.

Main Menu/View/Report. Opens the report viewer with the current report showing or a blank screen if there is no existing report.

Main Menu/View/ Open Report Viewer.

Opens the report viewer with a blank screen

The report is presented in two formats – Standard and HTML. When the report is run the report is automatically saved as a .VAR file and as an .HTM file.

The Report Viewer bases its fonts on those available on the user’s printer – in the same way a word-processor does. The report is still generated if no printers are installed but if the default printer is “Generic/Text Only” or similar then the report won’t generate properly as it will try to use a system text font.

6.13.1 Standard View When in Standard View the report can be navigated by using the left and right arrows to view the next/previous page. The report may be zoomed in and out by clicking on the magnifying glass , clicking on the arrow next to the magnifying glass and selecting the zoom level from the drop down menu, or by double clicking on the actual report page. The other options available when in standard view are; Open a new report and Print the report.

To print just the current page chose ‘Print’ and then chose ‘Selection’ from ‘Print Range’ options.

In Standard mode there are no editing facilities such as Find, Select All and Copy. However, these are available in the HTML view.

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Figure 6-14 Report Viewer – Standard View Please also note that the .VAR file displayed in Standard View is a proprietary file format that can only be viewed using ARCADY 6. You can email .VAR files to colleagues (no other files are required) as long as they have installed ARCADY 6. 6.13.2 HTML View The HTML report can be navigated by using the scrollbar to scroll up and down the page. Editing facilities such as Find, Select All and Copy can be found on the toolbar and also in the ‘Edit’ menu option. The HTML report may also be printed and print previewed.

Some HTML colours become transparent when printed - this can usually be solved by adjusting your browser settings. For example in Internet


Explorer go to Tools/Internet/Options/Advanced/Printing and tick ‘Print Background Colours’. However, the recommended method of printing from ARCADY is via the Standard View, since this will deal with page breaks and formatting automatically.

Using the HTML View allows you to copy selections and paste into any word processor, spreadsheet or similar.

Figure 6-15 Report Viewer – HTML View It should be noted that if you wish to publish the HTML report on the web or email it to a colleague you must attach/include all the bitmaps used in the report (which are stored in the same directory as the .HTM file and are given the same filenames as the report). We recommend zipping the .HTM file and bitmaps together to give a much more compact file that can be conveniently emailed. To facilitate this a number of menu options have been provided as described below: Main Menu/File/Open this report’s containing folder: Opens the Windows folder where the report is saved.

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Main Menu/File/Open this report in your default web browser: Launches your default web browser and loads this report. You can then close the Report Viewer and continue working in PICADY, switching to the last run report in your default web browser as necessary. Main Menu/Compact this report into a zip file: If you have a registered copy of WinZip installed on your PC (if not, see www.winzip.com to order or download), this option will create a zip file containing the report HTML file. all its associated graphic files, the input data file (.VPO) and output file (.VPO). The zip file can be saved or e-mailed, etc, allowing you to transfer reports without having to worry about the image files. Many zip file viewers allow the report to be viewed by simply opening the HTML file within a zip file, without having to extract the individual files. Main Menu/Zip and email this report: creates a zip file (as above), and, if you have a copy Microsoft Outlook installed, creates a new e-mail with the zip file included as an attachment. This is a very convenient way to forward reports to colleagues, together with the data file that was used to generate the report.

http://www.winzip.com/


6.14 Running the Graph Designer The new Report Designer is complimented by the Graph Designer which allows individual graphs to be plotted of certain output results against certain input parameters. The current data set is run through the analysis program several times with the selected x parameter varied over a specified range. The results from each run are then used to generate a graph of the selected output item against the varied parameter. For example, plotting a graph of Capacity against Entry Width would show how the capacity of an arm varies with the entry width of the arm.

All major geometric parameters can be plotted against a variety of ARCADY results, but some other parameters, such as geometric delay data are not be available.

All graphs are plotted by arm and time segment. Each arm is drawn in a different colour with different marker symbols for clarity. A key is provided on the graphs where necessary. The graphs can be included in the report and may be saved as part of a report template to be used again later. Any number of graphs may be opened at any time. The Graph Designer is accessible from the main toolbar Graph button (only when there is enough data to be able to run the analysis program), by selecting Main Menu/Run/Graph Designer, or from within the Report Designer when Add Graph or Modify Graph are selected.

Figure 6.16 Graph Designer

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Y axis items:

The list of items (click on the plus symbol to expand the list) that may be plotted on the y-axis. Depending on the item selected other selections (via two drop-down lists) may be required such as which arm and which time segment. Only parameters that are valid for the current data set are enabled.

X axis items:

The list of items (click on the plus symbol to expand the list) that may be plotted on the x-axis. Depending on the item selected other selections (via two drop-down lists) may be required such as which arm. Only parameters that are valid for the current data set are enabled.

Options: (see figure 6-17 Graph Designer Options) Allows user specification of graph titles, axis labels and axis ranges.

Figure 6-17 Graph Designer Options

Labels: Allows editing of the title, and x-axis and y-axis labels

Parameter range: The range over which the x-parameter will be varied and run through the analysis program. X-axis range:


The range shown on the x-axis. If Automatic is selected, the range is chosen automatically to fit the Parameter range. Otherwise, you may manually enter the desired range and interval parameters Y-axis range: The range shown on the y-axis. If Automatic is selected, the range is chosen automatically to fit the smallest and largest values produced by the analysis program. (These are not known until the graph is actually run.) If Automatic is not selected, you may manually enter the desired range and interval parameters.

Run Graph:

Runs the graph and displays it in a window. (See section 6.14.1 page 77) 6.14.1 Graphs

The graphs are plotted by arm with a small key included where necessary on each graph. The colours used for each arm match those used in the queue animations (see Section 6.11 page 60) Once a graph has been run it is opened in a new window which can be resized. There are various options associated with the graph that can be accessed by using a right mouse-click menu.

Figure 6-18 Graph

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The available menu items are: Menu Item

Function

Options Opens the Graph Options screen to allow editing of the title, labels and ranges.

Copy to clipboard Copies the graph, in meta-file format, to the clipboard.

Duplicate Creates a duplicate of the graph and displays it in a new window

Modify Opens the Graph Designer to allow complete modification of the graph.

Add to current report template Adds the graph to the current report template

Re-run graph Re-runs the graph – useful if any changes have been made to the current data set.

Close Closes the graph.

6.15 Viewing ARCADY text files There are two options on the ARCADY main menu for viewing ARCADY text files: View/View Input File and View/View Output File for the viewing of input data files and output data files respectively (see figure 6-7). The only difference between these two options is that the Viewer program displays the current input data file (if it exists) in the first instance and the current output data file (if it exists) in the other. If a file is not currently selected the Viewer will load without selecting a file to show.

Please note that the Viewer is a totally independent Windows program designed for viewing OSCADY and PICADY files as well as ARCADY files. It will display any ASCII text file by using the Viewer's own file selection menu.


Figure 6-19 Viewing Data When the Viewer is invoked through the GUI (it can be invoked outside the GUI) it will run concurrently with ARCADY. The Viewer can also be launched using View/Launch ASCII Viewer which launches the Viewer without selecting a file to show. Up to 12 files can be viewed simultaneously, with each file displayed within its own window within the main (MDI) window. Each of the open files can be accessed from Window/{Filename}. File/Refresh F5 allows the user to update the currently selected file in VIEWER with the current data in the data file (same as the Windows Refresh option). The windows can be tiled vertically or horizontally within the main window using Window/Tile and can also be cascaded using Window/Cascade. The text font for each window can be changed via the menu bar using Options/Screen Fonts.

Only non-proportional fonts should be used to view ASCII text files so that they are displayed correctly. The easiest way to ensure this, is to set Option/Use only non-proportional fonts on the main menu. This will restrict the screen font selection to those fonts available to the user which are non-proportional.

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The font selections and various options are stored in the Viewer’s options file so that they do not need to be set every time the program is run. 6.15.1 VIEWER features

The version of VIEWER supplied with ARCADY has five features to assist in the analysis of output files, many of which are new. These are: (i) The titles of each table in the output is highlighted in colour to make it easier to find

them. (ii) Each table can be accessed directly by selecting from the list of tables from

Data/{titles}. This option may be ‘synchronised’ for multiple files as long as all the open files contain the same set of tables.

(iii) The Edit/Find option or the Find button can be used to search for text strings within

the current document. (iv) The Edit/Copy option or the Copy button can be used to copy any selected text into

the Windows clipboard. (v) A compare facility is available so that two runs of ARCADY can be compared with

each other. The files to be compared should be opened in VIEWER. The currently selected file can be compared with another which is specified using the Main Menu/Edit/Compare File option. The differences between the files are displayed in different colours. To find the first and subsequent differences the Edit/Go to next difference option can be used.

(vi) A ‘What if I change this…’ compare facility is also available. The Edit/Compare

new run option, loads the current file from disk and automatically compares itself with the older version currently open within the VIEWER. To use this feature it is necessary to carry out the following actions: 1. run the data 2. use the VIEWER to look at it 3. switch back to ARCADY without closing the VIEWER 4. re-run the data with whatever changes you wish to make 5. switch back to the VIEWER 6. select Main Menu/Edit/Compare new run

The Edit/Compare Selections option allows the comparison of two sections of text instead of comparing complete files.


(vii) Comparing files is also made easier by using the synchronised scroll-bar on the

right-hand side of the VIEWER. This allows the user to scroll through all of the displayed files simultaneously. New to ARCADY, there are now several different ways to scroll:

Scroll Option

Operation

None

Synchronised scrolling disabled.

Scroll Up/Down

Via two buttons, allows up/down scrolling, five lines at a time. Useful if the files are not all the same length.

Match by ratio

Allows up/down scrolling via standard scrollbar. The scrollbar position is based on the ratio of the file length, so this option is recommended for files of the same length only.

Match by line number

Allows up/down scrolling via standard scrollbar. The scrollbar position is based on the line number of the file, so this option is ideal for synchronised scrolling through files that have similar information towards the start, but have different lengths because some files have extra data at the end of the file.

The scroll options are selected from Options/Synchronised scroll. (viii) The Edit/Go to same line option allows the matching of the position of one file to

the current position of another. (ix) Windows/Lock Window allows the currently selected window to be ‘locked’ or

‘unlocked’ so that an area of interest within the file can remain on the screen while the other files on the screen are scrolled through.

(x) The number of specific file types that the Viewer program has been designed to

view has been increased. Because of this, Options/Default file type can be used to set the default file type to either ARCADY/PICADY/OSCADY; TRANSYT or COBA/QUADRO.

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6.16 Printing ASCII text Printing can be carried out either directly from the GUI or via the VIEWER program. Using the VIEWER is the preferred option because of its additional ‘margin’ feature (see section 6.16.1). 6.16.1 Printing from the VIEWER

ARCADY files can be printed via the File/Print… option on the Viewer’s main menu. Before printing, a suitable printer font should be selected using File/Printer Options. Only non proportionally-spaced fonts should be used to ensure that the text files are printed correctly. The easiest way to ensure this, is to set the option Option/Use only non-proportional fonts on the main menu. This will restrict the printer font selection to the available non-proportional fonts. Separate screen and printer fonts can be specified by setting Option/Separate screen and printer fonts, otherwise the selected screen font is also used for printing. If the selected screen font does not have an equivalent printer font the program will use the nearest available printer font instead. The VIEWER program also allows margins to be set at the top, bottom, and left-hand side of the page. These are set from File/Print Options. This feature is particularly useful when output files are to be incorporated into reports. Control characters (“.”s in the first column) in the output file are interpreted by VIEWER as suitable places for page breaks. These are inserted by the analysis program at logical points in the output so that the output blocks are kept together if possible, and split in sensible places when necessary. A header, is printed at the top of each new page. The font selections, margin settings and other options are stored in the viewer’s options file so that they do not need to be set every time the program is run. A file can be printed by selecting the File/Print option and pressing the <OK> button. Multiple copies of the current file can also be specified for printing. 6.16.2 Printing from ARCADY

ARCADY input data files or output files can be printed via the File/Print option on the main menu of ARCADY. Before printing, a suitable printer font should be selected using File/Printer Fonts option. Only non proportionally-spaced printer fonts should be used to ensure that the text files are printed correctly. The currently selected printer font is stored in the options file. On selecting the File/Print option a window appears allowing ARCADY input, output and older DAT files to be selected for printing. Pressing the <OK> button, prints the file


and closes the window. Only one file at a time can be printed. When printing, each page number is displayed on the right-hand status box as it is sent to an internal buffer. The final page count is displayed once the printout has been sent to the printer. 6.17 Exporting output data In recognition of the fact that many users wish to carry out further analyses of the output data, ARCADY allows the queue and delay output data to be exported in a comma delimited format (a format that can be read into, say, a spreadsheet). To use this facility, first select Export output data… from the Main Menu to reveal the ‘Export output data’ window. Secondly, select the ARCADY output file from which you wish to extract the data. The default filename is the current output data file (if any). A browse button allows any output file to be chosen. Thirdly, specify whether to order the export data by arm or by time segment. Finally, press the <Export…> button to select an export filename. Any file extension is valid, but the default is a “.TXT” file.

Figure 6-20 Exporting Data 6.18 User Options ARCADY offers a variety of options that affect how ARCADY works. For convenience, these user options are accessed via a set of tabs within the same window. Each option is described separately in the following sub-sections.

6.18.1 General/Drive on the right

Select this option if you wish to model drive-on-the-right situations and leave blank for drive-on-the-left situations

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Figure 6-21 User Options: General

6.18.2 General/Automatically update output files in Viewer

When this option is set the program will tell the VIEWER program to re-load any currently displayed files. To make it easier to switch between the VIEWER and ARCADY make sure the VIEWER window is NOT maximised.

The VIEWER’s “Compare new run” facility will not work while this option is set, since it relies upon the original output file displayed in the VIEWER not being updated with the contents of the new output file.

6.18.3 General/Always display Progress Checklist

Select this option if you wish the Checklist to remain visible at all times. Normally, it would be hidden when a data-entry form is opened.

6.18.4 General/Automatically position Progress Checklist and data screens

When the ‘Always display Progress Checklist’ option is set, ARCADY can also be set to adjust the position of the checklist and the data-entry forms so that the two forms appear in the optimum position on the screen.

6.18.5 General/Suppress consequence warnings

Many data items determine what data is required subsequently and how they are entered. Because of this, it is often necessary to reset data back to their default settings when other related data is changed.


Therefore, whenever the junction data is edited ARCADY issues messages warning of the consequences. As the user gains confidence in the operation of the program the generation of these messages may become superfluous and can also become annoying. This option, when set, suppresses all “consequence warnings” that relate to data-entry.

Figure 6-22 User Options: File Options

6.18.6 File Options/Use same path for INPUT and OUTPUT files

When an input filename is changed the name of the output file is automatically set to the same name, but with a “.VAO” extension. If this option is set, the sub-directory of the output file is also automatically reset to the same as the input filename’s. If this option is not set, the sub-directory in which the output file will be saved, remains the same. This allows the input and output files to be kept together in one sub-directory or in separately sub-directories as required. 6.18.7 File Options/Use Windows style Open/Save dialogue boxes

When this option is set the program will display a standard file selection window instead of the default ‘ARCADY’ one when you use the normal left mouse-click on the LOAD DATA and SAVE DATA buttons. A right mouse-click can be used to temporarily switch to the type of dialog box which is not currently selected.

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6.18.8 File Options/“Save Data” request made when exiting

When this option is set the program prompts the user to save the current data before exiting the program. The data is saved to the currently selected file. 6.18.9 File Options/Location to store temporary files

This option allows the location to be set for the temporary storage of various files used by ARCADY. ARCADY, by default, will use the Windows temporary folder. Any alternative location specified by the user must have read/write access.

Figure 6-23 User Options: Graphs and Reports

6.18.10 Graphs and Reports/Expand arm names

If this option is selected arm names will be expanded to their full names (rather than 'Arm A', 'Arm B' etc) in both the Junction Diagram and any graphs generated using the Graph Designer.

6.18.11 Graphs and Reports/Number of analysis runs

This sets the number of steps to use when generating graphs. The x parameter is varied between its range through this number of steps, giving this many points on the resulting graph. A higher number of steps will give a more detailed graph, but the graph may take longer to generate.

6.18.12 Graphs and Reports/Show markers

If this option is selected the points plotted on the graphs will be indicated by markers, otherwise only the lines joining these points will be seen.


6.18.13 Graphs and Reports/Number of grid-line divisions

This sets the number of extra grid divisions to draw on graphs. E.g. if set to 4, each quarter-grid interval is shown. This applies to both axes.

6.18.14 RFC/Adjust the RFC threshold level used in the Report Viewer

This sets the RFC threshold level. Any Degree of Saturation values that are greater than this value are highlighted in red in the Queues and Delays table. In addition a bold line is overlaid on the ‘Degree of Saturation’ graph so that it can easily be seen if the RFC Level is exceeded at any time.

Figure 6-24 User Options: RFC 6.18.15 International/Use US Customary Units

If this option is selected the unit of measurement for distances is changed from metric to ‘decimal feet’, e.g. a tenth of a foot is shown as ‘0.1 (ft)’. The data is displayed and entered in decimal feet and the ARCADY report (defined by the Report Designer) displays decimal feet. However, the data in the ARCADY input file is always stored in metric units. 6.18.16 International/Use US Terminology

If this option is selected the standard UK terminology used in the graphical interface is replaced with terminology more familiar to users in North America.

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Figure 6-25 User Options: International

6.18.17 International/Vehicle Length

This options allows the vehicle length of a light vehicle/car (i.e. 1 PCU equivalent) to be changed. The distance represents the spacing of vehicles in a stationary queue from front bumper to front bumper. At the time of writing the ARCADY default is 5.75 metres. 6.18.18 Advanced/Calculate point-to-point delay

If this option is selected ARCADY calculates point-to-point journey times in addition to the standard geometric delay results. The option’s status can be saved as a default so that all new files have the same status.


6.19 Help system The ARCADY manual is also available in the form of a Windows help file. This help file is an invaluable reference tool that should be used in parallel with ARCADY. Special care has been taken to make sure that the contents of the manual have been faithfully reproduced and any necessary differences between the manual and the help file have been kept to a minimum. The following options are available via the Options Menu: 6.19.1 Contents

Selecting this menu option will load the ARCADY help file and display the contents page. The Help File consists of two windows – one displays a table contents (initially) and the other displays the help topics.

Figure 6-26 Main Help System

The table of contents window can display several different lists, which are accessible from the tabs at the bottom of the window (see figure 6-26). These are as follows:

i) CONTENTS displays tables contents

ii) SEARCH displays a list of every unique word in the main Help File. From this list, the user can search ARCADY Help using keywords which are associated with certain ARCADY topics.

iii) INDEX displays a list of key phrases that appear in the Help File.

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Access to these items are duplicated on the button bar on the Help Topics window. The buttons are self-explanatory.

6.19.2 Help tips

This option will load the ARCADY Help Tips file and display its contents page. This file contains a selection of additional tips in both the operation of the GUI and particular design concepts. An example screen is shown (see figure 6-27).

Figure 6-27 Help Tips

The Help Tips file will also be used to document changes to the operation of program that are a result of new releases of ARCADY. This means that the main Help File does not have to change for every release of the program and can continue to offer the same information as the published application guide.

6.19.3 About ARCADY

This shows the current version number of ARCADY. It also shows two release letters. The number plus the letters uniquely identify the release of ARCADY. The operating system the program thinks it is running under is also shown, e.g. Windows XP.


More details about the program can be accessed if required by opening the About Box, double clicking on the ARCADY icon, closing the About Box and then reopening it again. This will reveal details of the program release date as well as information on the program development team.

6.20 Leaving ARCADY To exit ARCADY the user can either select File/Exit from the main menu or use the main menu’s control box in its top left-hand corner. The program will ask the user to confirm the request to exit. If the “Save Data” user option is set, the user will be asked if the current data in memory (RAM) is to be saved. The data will NOT be saved unless the “Save data” option is set and the user chooses to save the data when prompted (see section 6.18.8, page 86). 6.21 Error messages Three types of error messages are generated by the ARCADY graphical interface: “specific”, “general” and “fatal”. Usually, “specific” error messages consist of a message or sequence of messages indicating what has gone wrong and why. They do not usually involve any user interaction other than to press the <YES> button and/or <OK> button in order to continue with the program, e.g. if an operation to read a data file fails because the file has become corrupted, messages similar to the ones shown (Figures 6-28 and 6-29) will appear. The program will terminate the file reading routine and pass control back to the user.

Figure 6-28 File error message

Figure 6-29 Extended file error message

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“General” error messages are more interactive in nature as their main purpose is to trap unexpected errors. These messages usually consist of an ARCADY error number, a description of the error type, and a set of three buttons - <IGNORE>, <RETRY>, <ABORT>. If the user selects <RETRY> the program will attempt to carry out the same operation as before. <IGNORE> allows the user to ignore the error message and proceed with the operation despite the error. Pressing <ABORT> allows the user to quit the program. A “fatal” error is one from which it has been decided that ARCADY cannot recover in any circumstance. A message box will inform the user that a fatal error has occurred. The message will display an ARCADY error message followed by the phrase “The program will now terminate”. The program terminates when the <OK> button is pressed. The GUI prevents the user from creating faulty data files during the data-entry process, but there are some errors that can only be detected during an analysis run. Therefore, the analysis program also generates a number of error messages and warning messages. These can be identified from their white background colour, a yellow exclamation mark or red cross in the centre of the message box (GUI messages have these to on side), and the product name in the title, i.e. “ARCADY 6”. Figures 6-26 and figure 6-27 are examples of typical warning and error messages.

Figure 6-30 Analysis warning message

Figure 6-31 Analysis error message

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7 Data Input 7.1 About this chapter This chapter describes how to input the data and describes the data that is required. A brief description of the input required is given for each item (shown in italics and written as they appear in the program). Where appropriate, this is followed by the allowable range for the item in question, also shown in italics.

Figure 7-1 Data Input Where more detailed information is available, the user is referred to the appropriate section(s). In particular, the methods of measuring the junction geometric and accident prediction parameters are contained in the Appendices. A series of windows (and frames within them) allow the user to enter the necessary information about the junction and the current run of the program. Details on the

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contents of each of these windows are given in this chapter while details on how the windows themselves operate is given in “GUI Operation” (section 6.5, page 51). Within this text, all references to particular ARCADY screens are made by quoting the window’s caption and frame caption (if any) which appears on the top left of each frame. Any references to ARCADY screen captures will use the user guide’s figure numbering system. 7.2 General data-entry conventions 7.2.1 Data-entry controls

Individual items of data are entered using edit boxes, option buttons, check boxes and scroll bars in the same manner as any typical Windows application. Data-entry can be achieved largely without the use of the mouse but the combined use of the mouse and keyboard is recommended.

7.2.2 Edit boxes with scroll bars

Many edit boxes are accompanied by scroll bars. The scroll bar on the right-hand side of an edit box will increase and decrease the value in the box by the smallest increment possible each time it is clicked, while the left-hand scroll bar (if any) will make larger changes; usually ten times larger than with the other scroll bar.

7.2.3 Range checking

All numbers that are entered are checked to ensure they are within their respective ranges. This check occurs when a control loses the focus, e.g. when the <OK> or <Cancel> buttons are pressed or the mouse or <tab> key is used to move to another control. If the value typed into the edit box is within its limits nothing happens, but if it is outside its allowable range three things occur: Firstly an error message tells the user that the value is outside its allowed range and shows the range of possible values. Secondly, the faulty data value is reset to its default value; and thirdly, the focus is moved back to the edit box to allow re-entry of a suitable value. Faulty data must be corrected before the window can be exited.

7.2.4 Consequence warnings

Many items of data determine what subsequent data items are required and how they need to be entered. Because of this, it is often necessary to reset data back to their defaults when other related data is changed. Whenever critical junction data is edited ARCADY will warn of the consequences of changing each value and will allow each change to be accepted or cancelled.

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7.3 Getting started To start an ARCADY input, edit, or run session, either click on the START button and select ARCADY 6 from the ARCADY 6 Start Menu or set up a short-cut to run VARCADY6.EXE. Once the main menu and checklist appears data-entry can begin. There is no requirement to specify an input data filename at this point. Data can be saved to a data file at any time during the data-entry process. The first item of data that needs to be entered is the Run Title. Clicking on the Run Information button on the Checklist will reveal the first data-entry window. Each window is described in the following sections. 7.4 Run Information

Figure 7-2 Run Title The following Run Information is compulsory: Run Title: Enter any title, up to 80 characters, to be used for identification of the run (see figure 7-2). It will be printed at the top of each page of output. range 0-80 alphanumeric characters

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The following Run Information is optional: Location: Enter any text, up to 60 characters, to describe the location of the site being modelled.

range 0-60 alphanumeric characters Client; job number; enumerator: Enter any text, up to 40 characters for each item, to record pertinent information about the data file.

range 0-40 alphanumeric characters Date: This can be used to associate a particular date with the data file, e.g. the date the file was prepared.

“dd mmm yyyy” formatted

Status: Allows the user to indicate the status of the file, either by selecting one of the pre-defined phrases or by entering their own.

range 0-20 alphanumeric characters Description: Allows the user to add a longer description on multiple lines.

alphanumeric characters

7.5 Parameters Start Time: & End Time: Enter the start and finish times of the required modelling run (see figure 7-3). If modelling a traffic peak it is important to include some off-peak time either side of the peak. This is to ensure that the assumption, by the program, that queues at the start and end are zero is reasonable. Flow information for the specified period will be required later. range 0000-2400 (24 hour clock)

Figure 7-3 Modelling Parameters

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The period must be compatible with the flow information to be provided. For example:

a) If demand flows are to be specified using the LEVELS method

(section 4.9.1, page 26) the period must start before the flow on any arm starts to rise, and end after the flow on any arm ceases to fall.

b) If demand flows use the FOUR method (section 4.9.3, page 28) the

modelled period can only be the four hours for which the demand flows are provided.

c) If demand flows are to be specified using the ODTAB method

(section 4.9.4, page 31) the modelled period must be 90 minutes - specifically the one hour period for which the O/D flows are provided plus 15 minutes either side of it.

Interval: Enter the segment length into which the whole modelled period is to be split. The modelled period must be a whole number of segments. Note that all flows (and therefore capacities) are assumed to be constant throughout a time segment. For this reason the segment length should not normally exceed 15 minutes, particularly if modelling a peak period, otherwise this underlying assumption would (usually) be unreasonable. Also, the segment length should not normally be less than 5 minutes, because very short segments involve a high random variability of flows from one time segment to the next. range 1 to 30 minutes 7.6 Junction type and arm names

Figure 7-4 Junction Type

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Roundabout Type: i) Chose whether a standard roundabout or mini-roundabout is to be modelled. ii) Enter the number of arms on the roundabout to be modelled (see figure 7-4).

It is important to set this correctly since the data required for a mini-roundabout is different from that of a standard roundabout.

Arm Names: Enter any name for each arm of the roundabout (used for identification purposes when studying the output). Note: In drive-on-the-left mode arms are labelled clockwise A, B and C, where arm A is usually the first arm clockwise from 12 o’clock. For drive-on-the-right mode the arms are labelled in a counter-clockwise direction starting with the first arm anti-clockwise of 12 o’clock. range 0-80 alphanumeric characters (Traffic) Flow Scaling factor (%): Enter the scaling factor to be applied to each arm of the junction. The scaling factors, by default, are set to 100% of the flows specified. e.g. to double the flows enter 200. The scaling factor affects both the accident and demand data for all demand sets. range 0 to 300 Located in Greater London: Specify whether the junction is in London or not. (Accident frequencies in London exhibit unique differences to those of the UK as a whole. Y/N Junction Image: Optionally, select an image to associate with the data file. Having selected an image, it is stored in the same directory as the input data file as a “.VAJ” file using the data file name. The chosen junction image can be embedded into ARCADY’s graphical output using the Graph Designer. The <Clear Picture> button allows the image to de-selected, while the <Enlarge> button allows the user to see the full-size version of the image instead of just the thumb-nail version.

Accepted formats: bmp, jpg, gif ,wmf, emf

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7.7 Demand type (principal options)

Figure 7-5 Demand Type

Traffic Demand Data Type: Choose one of the five options according to the type of flow data available (see figure 7-5). Note that the first four options are listed in order of the amount of information required from the user and, consequently, the accuracy and reliability of the results. The four methods of supplying flow data are described in Section 4.9, page 26. If any of the four options are incompatible with the model period (start and end times) they will be unavailable. The “saturation” option is a special feature which simply predicts the maximum capacity of the junction for the given turning proportions. No demand flows are required to use this option (section 4.9.5, page 33).

Queue variability analysis is not possible with the DIRECT option, because it depends on the demand flow profile being a Normal distribution.

7.8 Principal options Some of the options in this window will be disabled. Such options will have become logically incompatible because of information already supplied in the previous windows (see figure 7-6).

Geometric Options/Geometric Delay and Capacity Relationships principal

options are not needed for mini-roundabouts.

Geometric Options/Geometric Delay: Specify whether or not geometric delays are to be calculated. If so, the program will need extra data that is relevant to geometric delay (Section 4.3, page 18). Y/N

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Geometric Options/Geometric Data same for all arms: Specify whether the geometric data is the same for all arms of the roundabout. If the junction is completely symmetrical, it will only be necessary to enter geometric data for one arm. Y/N Heavy Vehicles/Default Proportions: Specify whether the percentage of heavy vehicles is to be provided by the user, or whether a single default value (10 percent) is to be assumed by the program. If provided by the user, the proportions are allowed to vary by entry arm and/or time of day if the information is available (section 4.10, page 34). Y/N

Figure 7-6 Principal Options Heavy Vehicles/Vary over time: Specify whether or not the percentage of heavy vehicles varies with time. If so, the user will be asked to supply individual values for each time segment. This option is not available if default proportions have been selected as the default percentage is constant with time. Y/N

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Heavy Vehicles/Vary over turning movement. Specify whether or not the percentage of heavy vehicles varies with turning movement. If so, the user will be asked to supply individual values for each turning movement. This option is unavailable if default proportions have been selected. Y/N Capacity Relationships/Grade-separated or large roundabout (>130m diameter). Specify whether there are any grade-separated entries to the roundabout or, for an at-grade roundabout, that it has a maximum overall diameter greater than 130 metres. If either of these cases is true, the capacity relationships for the roundabout as a whole will be different from that of a “conventional” roundabout (section 4.7, page 23). Y/N Capacity Relationships/Estimate initial circulating flows from demand data. Specify whether the program is to estimate the roundabout's circulating flows from the supplied demand data. Circulating flows (estimated or otherwise) are only required if the "Grade-separated entries" option is set, and can be estimated by the program only if DIRECT or ODTAB demand data is entered, and turning proportions are neither default nor calculated from entry/exit counts. When an analysis run is requested, if this option is set the program will ask the user to confirm that they wish to calculate new circulating flows from the demand data. The current circulating flows (if any) will be overwritten. Y/N

ARCADY only provides the initial estimates of “CIRFLO”. It takes no account of the potential differences between the demand data provided and the amount of traffic emerging from each arm. Details on how to provide improved estimates are described in Appendix H, page 239.

Having run ARCADY once to estimate the initial circulating flows a second run of the program is necessary to make use of these values, i.e. the first run only calculates the initial values; it does not use then in the capacity calculation (see Appendix H for more detail). This is because the user is advised to check the calculated values before using them to ensure they are sensible for the junction being modelled.

Lighting: If modelling a standard roundabout… Specify whether the queue/delay calculations are to be based on night time or daylight conditions. Capacities are taken to be five percent lower in dark conditions than in daylight conditions (section 4.12, page 35). If modelling a mini-roundabout…

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Specify whether the queue/delay calculations are to be based on ‘normal’, daylight, or night time conditions (section 4.12, page 35). Normal/Daylight/Night time Road surface. (mini-roundabouts only) Specify whether the queue/delay calculations are to be based on ‘normal’, dry, or wet surface conditions (section 4.12, page 35). Normal/Dry/Wet Site specific data/flow data: These refer to the option within ARCADY whereby the user is able to apply a site specific capacity correction to one or more arms of the roundabout (section 4.6, page 22). Measured values of mean entry flow and mean circulating flow for one or more arms of the roundabout can be entered during an initial program run. The measurement must be made only during periods when there is continuous queueing on entry. This does not usually apply to the whole modelled period. To enable this facility select “Site specific flow data”(“Site specific interception” will be de-selected automatically by the program as both options cannot be set). The program uses the site- specific information to calculate intercept correction(s) and then automatically makes use of them in its calculations. The intercept corrections should then be used for all subsequent runs with the junction (section 5.7 and 7.15, page 45 and 114). Y/N

If the site-specific corrections have been subsequently edited manually, the original site-specific corrections can be re-calculated by re-selecting the “Site specific flow data”. (The site-specific data is retained in ARCADY 6).

Site specific data/Intercept correction: After the first run, the program automatically de-selects the “Site specific flow data” and sets the “Site specific intercept correction” option instead. For all subsequent runs using the site specific intercept values, these two options should be set this way. Y/N

If applying flow data corrections, it is important that the junction geometry specified in this initial correction run of the program is the same as the layout on the road when the measurements were made. Small changes to the junction

geometry can then be made during subsequent runs of the program with an applied intercept correction - this correction should still be applicable to the modified junction.

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Other Options/Accident Analysis: If modelling a standard roundabout specify whether accident frequencies are to be predicted. If so, they can be predicted for any or all arms of the roundabout, providing sufficient information is available. Y/N Other Options/Simple Accident Analysis (M0): or Other Options/Full Accident Analysis (M2): If modelling a mini-roundabout specify whether either simple or full accident predictions are to be calculated. The simple model is predicts accidents purely on traffic flows. The full model requires considerably more junction data to be provided in addition to traffic flow data, but will provide more accurate results. Y/N Other Options/Queue-length variations: Specify whether daily queue variations are required in the output (as described in section 4.2, page 17). This option also allows the program to report on the probability of queues reaching back to a user-specified queue marker or beyond. This option is unavailable if the DIRECT option is used to specify demand flows. Y/N Other Options/Marginal Analysis: Specify whether marginal analysis is required in the output. With this option set ARCADY predicts the effects (on capacities and accidents) of small changes in flows or junction geometry (section 4.8, page 24). Y/N Turning Proportions/Default used: Specify whether or not default turning proportions are to be provided by the program. Default values are obtained from Table 4.1 (section 4.10, page 34). They should only be used as a last resort - being “global” averages they may well be very inaccurate for a particular junction. If turning proportions are to be provided by the user they may vary by entry arm and/or time of day. Y/N Turning Proportions/Vary over time: Specify whether or not the turning proportions vary with time. If so, the user will be asked to supply individual turning proportions for each time segment. N.B. This option is unavailable if default turning proportions are specified since the program assumes that the default turning proportions are constant with time. Y/N

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Turning Proportions/Vary over entry: Specify whether or not the turning proportions are different at each of the roundabout entries. This option is unavailable if default turning proportions are specified since the program assumes that the default turning proportions are constant with entry. If an origin-destination table (ODTAB) is being used to provide the demand flows this option will be set because individual turning proportions from each entry are implicitly given by the O-D table. Y/N Turning Proportions/Calc from entry and exit counts: Specify whether or not the turning proportions should be derived from entry and exit counts (using a Furness balancing technique). If so, the user will be asked to enter exit flows for each arm of the junction, by the same method as demand flows are provided. If an origin destination table (ODTAB) is being used to provide the demand flows, then this option will be unavailable because individual turning proportions from each entry are implicitly given by the O-D table. Y/N

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7.9 Geometries, queues and capacities The geometric window contains a series of different frames representing different sets of data (see figure 7-7). The frames are accessed using the toolbar along the top of the geometric form – one button for each frame Some frames are not required because options selected in previous forms have determined that these frames are no longer needed, in which case, the relevant buttons will be disabled. If data is needed for each arm separately, such as in the case of geometric delay data, a frame containing the buttons <Next Arm> and <Previous Arm> allows the user to switch between arms. The most efficient way of entering data is to enter the data for every arm before moving on to the next frame. 7.10 Arm geometries Most values used for the junction geometry must be within the range over which the ARCADY model was originally calibrated. If any of them are not, the program may still run successfully, but a warning message will be printed in the output, informing the user that the outlying value has been changed to an acceptable value. For most data values the GUI restricts the values entered to their calibrated limits. (For details of warning messages, section 8.6, page 173.) 7.10.1 Standard roundabout (Arm Geometries)

Figure 7-7 Standard Roundabout (Arm Geometries)

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The Arm Geometries frame for standard roundabouts is shown in Figure 7-7. Approach road half-width (m): This is the approach road half-width, upstream of any entry flare. range 2.0 to 12.0 Entry width (m): The entry width of the arm must be greater than or equal to the approach width. range 3.0 to 16.0 Effective Flare length (m): If there is no flare (i.e. Entry width = Approach road half-width), the flare length should be set to zero. range > 0.0 Entry radius (m): This is the minimum radius of curvature of the nearside kerbline at entry. range 30.0 to 100.0 Inscribed circle diameter (m): This is the diameter of the largest circle that can be inscribed within the junction outline. range 13.0 to 327.6 Conflict (entry) angle (degrees): This serves as a geometric proxy for the conflict between entering and circulating streams. Also known as entry angle, and is not to be confused with geometric delay entry angle. range 0.0 to 80.0 Exit from roundabout only: Specify whether the arm in question is one-way leading away from the roundabout. Y/N Details of how to measure the above geometric parameters are given in Appendix B, page 215.

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7.10.2 Mini-roundabout (Arm Geometries)

Figure 7-8 Mini-Roundabout (Arm Geometries) The Arm Geometries frame for mini-roundabouts is shown in Figure 7-8. Approach road half-width (m): This is the approach road half-width, upstream of any entry flare. range 2.0 to 10.0 Minimum approach road half-width (m): This is the minimum half-width, measured anywhere within the final 100 metres of the approach. range 2.0 to 10.0 Effective Flare length* (m): Enter the average effective flare length. If there is no flare, the flare length should be set to zero. range 0.0 to 45.0

* Not measured in the same way as for standard roundabouts – construction uses minimum approach road half-width.

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Entry width (m): The entry width of the arm must be greater than or equal to the approach width. range 3.0 to 10.0 Distance to next arm (m): Enter the straight line distance from the offside end of the give-way line to the nearest point of the median marker or island on the next arm. range 5.0 to 20.0 Entry corner kerb line distance (m): Enter the length of the entry corner kerb line, measured from a point on the entry kerb to a point on the exit kerb of the next arm clockwise. range 2.0 to 40.0 Gradient over 50m (%): Enter the gradient of the arm. It is the average gradient over the last 50 metres prior to the junction. Negative values indicate that the gradient is downhill, and positive values indicate that the gradient is uphill, on the approach towards the junction. range -7.0 to 7.0 Kerbed central island: Specify whether or not there is a kerbed central (refuge) island within the final 20 metres of the approach. Y/N Details of how to measure the above geometric parameters are given in Appendix B, page 215.

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7.11 Circulating flow and separation (CIRFLO and SEP) If the roundabout has been specified as grade-separated this frame will be accessible. This additional data is used for the calculation of the capacity relationship. (See figure 7-9.) Circulating flow: (CIRFLO) The circulating flow required (CIRFLO) is the mean rate of flow (in PCUs per minute) circulating past the arm in question during the central 30 minutes of the total period being modelled. The mean should be based on several days measurements. Naturally, the individual days on which flows are measured, for inclusion in the mean, should be representative of the situation being modelled, e.g. if modelling a weekday peak, CIRFLO would ideally be the mean taken from all five weekdays equally represented. For details of how to estimate CIRFLO when it cannot be measured, see Appendix H, page 239. range > 0

Figure 7-9 Circulating flow and separation Entry-to-Exit separation: (SEP) SEP is the distance (in metres) between the entry point of the arm in question onto the roundabout, and the exit point of the same arm from the roundabout. It is only applicable where the entry and exit for the particular arm are separated by a significant length of circulating carriageway. For arms that are not, enter zero for this parameter. Details of how to measure it are given in Appendix B, page 215. range > 0

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When the entry (on-ramp) and exit (off-ramp) of a particular arm are not adjacent, i.e. ‘in effect’ it is an entry-only arm, the separation should be measured between the centres of the entry and the previous ENTRY (on the previous arm). If the separation is greater than 160 metres, 160 should be entered.

7.12 Pedestrian crossing and demand type Crossing type: Specify whether or not there is a zebra or pelican crossing on each arm of the junction.

ARCADY 6 has a new, more accurate, Pelican Crossing model allowing the capacity and delay effects of signal-controlled crossings on both standard roundabouts and mini-roundabouts to be calculated. By specifying full details of the operation of a Pelican crossing, users can achieve improved results when compared with the ARCADY 5 Pelican Model which was also limited to mini-roundabouts. Other types of signal-controlled crossings, such as Puffin crossings (Pedestrian User-Friendly INtelligent), may have different capacity and delay effects, and therefore cannot be modelled.

Figure 7-10 Pedestrian crossings

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For each crossing that exists, specify one of the three demand types (see figure 7-11). Direct: With this option, pedestrian flows across the pedestrian crossing on this arm must be entered explicitly for each time segment. Constant: With this option, pedestrian flows are assumed to be constant throughout the total modelled period. A single value for the rate of flow will be requested from the user later. Profile as for vehicle demand on link: With this option pedestrian flows are assumed to vary in time in the same way as vehicle flows. A single average pedestrian flow rate for the total modelled period will be requested, which will be used to synthesise a profile of the same shape as the vehicular demand profile on the same arm. 7.13 Geometric delay data This frame will be accessible if geometric delay calculations were requested in the “Principal options” form (See figure 7-11).

Figure 7-11 Geometric Delay

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Sight distance to right (m): Enter the visibility to the right (exit-only arm = 0.0). If this is not known, it should not be guessed at; enter zero instead. ARCADY will then use a revised model which does not require it. range 0.0 to 100.0 Angle between arm [n] and [n+1]: Enter the angle between the current arm and the next arm clockwise measured on the approach to the roundabout. The sum of the angles between arms around the roundabout must equal 360 degrees. Entry link speed (kph): The speed of traffic approaching the junction is measured at a point on the arm far enough away from the junction for it not to affect the traffic speed. Where new roads and junctions are being assessed, the appropriate speed may be estimated by use of speed/flow curves described in COBA10 (UK DEPARTMENT OF TRANSPORT et al ,1996). (For an exit-only arm set this to zero.) range 0.0 to 99.0 Exit link speed (kph): The speed of traffic departing from the junction should be measured or estimated in a similar manner to Entry Link Speed. range 0.0 to 99.0 Entry/Exit angle (degrees): Enter the entry and exit angles of the arm in question (The Entry angle is set to 0.0 for exit-only arms). range 0.0 to 90.0 Distance from centre to Entry/Exit (m): (The Distance from centre to Entry is set to 0.0 for exit-only arms.) range 0.0 to 200.0 Exit Radius into (m): Enter the exit radius into the arm in question. range 0.0 to 100.0 Details of how to measure the above geometric delay parameters are given in Appendix C, page 223.

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7.14 Distances through junction (“Delay 2”) This frame will be accessible if geometric delay calculations were requested in the “Principal options” form (See figure 7-12).

Figure 7-12 Distances through junction Enter the distance (in metres) from each arm (source) to each other arm (destination), measured along a typical path taken by a vehicle making the turning movement, from the junction entry to the junction exit. Use the <Previous Arm> and <Next Arm> buttons to change the ‘source’ arm. ARCADY automatically prevents the entering of this data for exit-only arms. range > 0.0 Distance included upstream/downstream (m): If point-to-point delay calculations have been requested, enter the distance upstream and downstream on each arm from which the point-to-point journey time is measured. If the value used is exceeded by the internally ‘calculated value an error message will be displayed. If this happens you should increase the distance until the messages disappears.

range 10.0 to 500.0

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7.15 Site-specific observed flows This frame needs to be used if “site-specific flow data” was specified in the “Principal Options” window (see figure 7-13). Observed flows can be specified for the arms for which observed data is available.

Figure 7-13 Site-specific observed flows For details of how to carry out the necessary measurements on-site, see Appendix D, page 227. Mean flow for arm n (ENTRY and CIRCULATING): Enter the mean entry flow and the mean circulating flow (pcu/min) for each arm, from measurements made on site, for which this information is available. The program will use this information to calculate intercept correction(s) for each arm that data is provided for. ARCADY automatically generates its final results using the calculated intercept corrections. Subsequent runs of ARCADY will also make use of the intercept correction terms. range > 0.0

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7.16 Site-specific correction terms This frame becomes accessible if “site-specific intercept correction” was specified in the “Principal Options” window (see figure 7-14).

Figure 7-14 Correction data Correction term for arm n: Enter a capacity correction value for each arm. The correction terms can be calculated by ARCADY using observed flows or by entering the correction factor directly. range +ve or –ve

ARCADY 6 retains the site-specific observed flow data in the current data file even after the calculation of the correction factors, so it no longer offers the user the (ARCADY 5) option to save the site-specific corrections to different data file. The observed data is accessible if either “Site-specific flow data” or “site-specific intercept correction” is set in the ‘Principal Options’ screen. Re-selecting the “site-specific flow data” option and re-running ARCADY will re-calculate a new set of correction factors using the current site-specific observed flow data.

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To summarise the actions of ARCADY: Any run of ARCADY while “site-specific flow data” is set will firstly, generate site-specific correction factors which will be used to calculate the final output results and secondly, de-select the “site-specific flow data” option and set the “site-specific intercept correction” instead.

Any run of ARCADY while “site-specific intercept correction” is set will use the site-specific correction factors to calculate the final output results and will ignore any site-specific flow data whether or not it exists. 7.17 Queue length variations If “Queue variations” has been specified in the ‘Principal Options’ window Queue Markers can also be specified.

Figure 7-15 Queue length variations Queue Marker for arm A: Specify whether or not a queue marker is required for the arm in question (section 4.2, page 17). If so, the program will predict the proportion of occasions on which the queue on each arm will extend beyond the marker. Y/N The information can be entered for any/all arms as required.

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Distance from give-way line (m): For the arms for which a queue marker has been specified, enter the distance the queue marker is from the flare in metres (or give-way line, if no flare exists). Note: On a flared arm, the queue marker must be upstream of the flared section. range 0 to 999 (integer) Flare storage (PCUs): For the arms for which a queue marker has been specified, enter the normal storage capacity (in PCUs) of the flared area up to the give-way line. If no flare exists, the flare storage is set to zero. range 0 to 999 (integer) For details of how to carry out the necessary measurements see Appendix E, page 229. 7.18 Vehicle flow data (demand data) The Demand Data window consists of up to four different frames depending upon the options chosen in the “Principal Options” window. The first of these frames, ‘Demand Sets’, allows the specification of multiple demand sets – one of the new features of ARCADY 6. The advantage of multiple demand sets is that the flows, vehicle proportions, etc can be varied in each set. This can be used to represent background flows and additional flows attributed to, say, land development or traffic growth. The flows can then be run together (the flows summed) with the output being written into one report. It can also be used simply to store multiple sets of flows ready to be selected and run separately. This reduces the number of input files required. (See Section 7.18.2, page 118 for more information on using multiple demand sets.) The second of these frames, which is always needed, is used to enter the vehicular demand data. This data can be input in one of four ways (DIRECT, LEVELS, FOUR and ODTAB) again according to the method chosen in “Principal Options”. These alternative methods are fully described in Section 4.9, page 26. The methods of data-entry for the four alternatives are outlined in the following sub-sections. 7.18.1 How to use the Demand Data window

Two additional frames become available depending on the options chosen in the “Principal Options” form: If default heavy vehicle proportions are not chosen the program requires more data to be entered via an additional frame (section 7.20, page 125) Another frame is also needed to enter turning proportions if default turning proportions have not been chosen (section 7.19, page 124).

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The demand data frames can be accessed in any order by clicking on the appropriate button. Alternatively the ‘STEP by STEP’ button as seen in Figure 7-16 can be used which will go through each data entry screen in turn, which encourages a structured approach to entering the data and helps to avoid any data being missed out. If any item is set to vary by time segment, clicking on the ‘STEP by STEP’ button will move the frame on to the next segment. After the last segment has been reached the next click will take you to the next frame that is required, and so on until the program returns to the ‘Demand Set’ frame again.

Figure 7-16 Demand Data Navigation Because of the amount of data and the considerable number of possible variations in the type of data required and hence the layout of each frame, the edit boxes are set out in the form of a grid. To move around the grid from cell to cell there are three options; use the mouse to click on each cell; use the <tab> key; or use the Cursor keys. The data values can be entered either by typing the values into the grid boxes or by using the <PgUp> and <PgDn> keys to increment and decrement the values. If data for each time segment (interval) is required the <Copy Current Segment to All> button can be used to copy all the flows from the current segment to all the others. If exit flows are required the <Copy Entry Flows to Exit Flows> button can be used to copy all the entry flow values to exit flows. 7.18.2 Using Multiple Demand Sets

The ‘Demand Sets’ frame consists of two list-boxes and six buttons (see Figure 7-17) The first list-box lists all existing demand sets whereas the second list-box lists all the chosen demand sets. The traffic flows of the selected flows are summed prior to being analysed. For example you may have three existing demand sets but only wish to combine two of them.

If you don’t want the flows of the demand sets summed choose just one demand set at a time and remember to rename the file each time if you wish to retain the output from each run.

The following table describes what each button does: Button Function

Data Input Page 119

New Set Creates a new set.

Copy Set Creates a copy of the currently highlighted set (i.e. Copies all flows, vehicle proportions, turning proportions etc into the new set).

Edit Title

Allows the demand set titles to be changed.

Delete Set

Deletes the currently highlighted set. N.B. this deletes all the demand data associated with the set.

Select

Adds the currently highlighted demand set to the list of sets to be run through the analysis program (Alternately the same result may be produced by double clicking on the demand set to be added.)

Remove

Removes the currently highlighted set from the list of sets to be run through the analysis program (Alternately the same result may be produced by double clicking on the demand set to be removed.)

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Figure 7-17 Demand Sets

The demand set which is currently selected in the top list-box is the one which is accessed when pressing any of the other buttons on the button bar.

7.18.3 DIRECT data

Figure 7-18 DIRECT data Direct Entry Flows: Enter the flow arriving on each arm, for each time segment, in vehicles per minute. Use the <Previous Time> and <Next Time> buttons to access each time segment (see figure 7-17). The <Copy Current Segment to All> button can be used to copy data from the segment currently being viewed to all other segments. If exit flows are required the <Copy Entry Flows to Exit Flows> button can be used to copy all the entry flow values to exit flows.

range { Flow > 0.0 } 7.18.4 LEVELS synthesised profile

Data Input Page 121

Figure 7-19 LEVELS data Time (Rising, Peak and Falling): Enter the times at which the flow starts to rise, reaches a peak, and ceases to fall, on the arm in question (see figure 7-19). These times are referred to as t1 (rising time), t2 (peak time) and t3 (falling time) in section 4.9.2, page 27, and are shown in Figure 4-1.

ranges {t1 > modelling start time}; {t2 > t1} {t3 > t2} and {t3 < modelling end time}

Flow (Rising, Peak and Falling): Enter the flow levels (vehicles per minute) at times t1, t2 and t3. These are referred to as q1 (rising flow), q2 (peak flow) and q3 (falling flow) in section 4.9.2, page 27. and are shown in Figure 4-1.

ranges {q1 ≥ 0.0}; {q2 > q1} {q2 > q3} and {q3 > 0.0 }

Times same for ALL arms: Specify whether the times given above are applicable to all arms. If so, the user only needs to enter the “rising”, “peak” and “falling” times for arm A. The times for the other arms will be inserted by the program automatically. Y/N

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7.18.5 FOUR synthesised profile

Figure 7-20 FOUR data Traffic counts arriving at junction for 4 one-hour periods: Enter the hourly flow counts (vehicles per hour) over four one-hour periods for traffic arriving on each arm of the junction (see figure 7-20). Details of this method of deriving the flow profile are given in Section 4.9.3, page 28. If exit flows are required the <Copy Entry Flows to Exit Flows> button can be used to copy all the entry flow values to exit flows.

range { Flow > 0.0 }

The greatest flow on every arm must occur in the second or third hour.

Data Input Page 123

7.18.6 ODTAB Origin destination table

Figure 7-21 ODTAB data Turning Counts (vehicles in 1 hour period): Enter a single hourly flow count for each origin-destination (see figure 7-21). When using this method of specifying demand flows, it is only possible to model a total period of 1½ hours. The single hourly flow specified in this matrix should be for the central hour within the 1½ hour modelled period. Flow rates for the 15 minutes either side of the central hour are derived by the program. Details of this method of deriving the flow profile are given in section 4.9.4, page 31.

range { Flow > 0.0 }

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7.19 Turning proportions (demand data) This frame is needed to enter turning proportions if default turning proportions have not been chosen in the “Principal Options” form. It is accessed via the <Turning Proportions> button in the “Demand Data” form (see figure 7-22). Note: this frame will not appear if: i) the origin-destination table method (ODTAB) is used to specify demand flows

(since the turning proportions are implicitly provided in the O/D matrix). ii) turning proportions are to be derived from entry/exit counts as specified in

“Principal Options”. See section 7.19.2, page 125.

Figure 7-22 Turning Proportions 7.19.1 Turning Proportions (or counts) arm-to-arm

Enter the turning proportion (or count in vehicles) from each arm to each other arm. If turning proportions are specified as varying over time in “Principal Options” <Previous Time> and <Next Time> buttons will be enabled so that turning proportions can be entered for each time segment and the <Copy Current Segment to All> button can also be used to copy data from the segment currently being viewed to all other segments.

range > 0.0

Data Input Page 125

If the numbers in each row sum to approximately unity, they are assumed by the program to be proportions rather than counts - in which case the numbers in each row are adjusted pro-rata, so that each row sums to exactly unity.

Mixing of proportions and counts in this table will give rise to serious errors since the analysis program will treat the proportions as actual counts.

7.19.2 Turning Counts Derived from Entry/Exit counts

Enter exit counts in the same way as the demand flows (DIRECT, LEVELS and FOUR options only). Frames which are derivatives of the entry flow frames will request the exit flows. The <Copy Current Segment to All> button can be used to copy data from the segment currently being viewed to all other segments. The <Copy Entry Flows to Exit Flows> button can be used to copy all the entry flow values to exit flows. An example of one of the derivative frames is shown below (see figure 7-23).

Figure 7-23 LEVELS Exit flows

7.20 Heavy vehicle percentages (demand data) If default heavy vehicle proportions are chosen, a 10% value is used throughout. If better data is available, it is entered via an additional frame. The frame is accessed through the <Next...> button on the “Demand Data” form, (see figure 7-24).

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Figure 7-24 Heavy vehicle percentages The data that is requested by the program depends upon whether the percentage of heavy vehicles is specified in the “Principal Options” window as varying over time and/or turning movement. If the proportions vary over turning movement an O-D table, similar to that used in the ODTAB Demand Data option, will be used to enter the data for each movement. If the proportions vary over time the <Previous Time> and <Next Time> buttons are used to enter data for each time segment. range 0.0 to 100.0 7.21 Pedestrian crossing data A frame requesting input data will appear for each arm for which a zebra or pelican crossing has been specified, (see figures 7-25 and figure 7-26). Sections 7.21.1 and 7.21.2 detail the data required respectively. Pedestrian flow data is required for both types of crossing as described in section 7.21.3

Data Input Page 127

Figure 7-25 Geometric data for Zebra crossing 7.21.1 Geometric data for a Zebra crossing

Enter the geometric data relating to the unsignalised ‘Zebra’ crossing on each arm. A more detailed description of how to measure these parameters is given in Appendix F, page 231. Space between crossing and junction entry (vehicles): Enter the numbers of vehicles which can be held in the space (in all lanes) between the crossing and the junction entry (see figure F1-1).

range > 0.0 Space between crossing and junction exit (vehicles): Enter the number of vehicles in a queue at the pedestrian crossing on an exit from the junction which would reach back far enough to block half of the previous junction entry (see figure F1-1).

range > 0.0 Length of crossing (entry and exit) (m): Enter the length of the pedestrian crossing. If there is a central refuge enter two lengths, one corresponding to the part of the crossing across the junction entry and a second for the junction exit portion.

range > 0.0

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7.21.2 Geometric data for a Pelican crossing

Enter the geometric data relating to the signalised ‘Pelican’ crossing on each arm. A more detailed description of how to measure some of these parameters is given in Appendix F, page 231. Amber time preceding a red period (s): Enter the amount of amber time shown to drivers before a red signal is shown.

range > 1.0 Amber time which can be regarded as green (s): Enter the amount of time (on average) that vehicles continue to pass through the crossing during the amber time that precedes a red period.

range > 0.0

Time between traffic light turning red and ped. signal appearing (s): range > 1.0

Time period green man signal is shown (s): Enter the time that the ‘green man’ signal is shown to pedestrians, excluding the ‘flashing green man’ time period.

range > 4.0

Time period flashing amber traffic signal (s): range > 6.0

Minimum period traffic signal remains green after a red period (s):

range > 6.0

Reservoir space between crossing and junction entry: Enter the numbers of vehicles which can be held in the space (in all lanes) between the crossing and the junction entry (see figure F1-1).

range > 0.0

Data Input Page 129

Figure 7-26 Pelican Crossing Data

7.21.3 Pedestrian flow data for a pedestrian crossing

Enter the average rate of flow per minute of pedestrians using the crossing. If the pedestrian flow profile is specified as varying in the same way as the vehicular flow profile (see “Principal Options” window) the pedestrian flow rate will be calculated by the program for each time segment, based on the average rate specified.

range > 0.0 (if using the DIRECT option)

If the DIRECT option of specifying pedestrian flows was chosen in the “Crossings” frame of the “Geometric Data” window, the frame will look like figure 7-26. For the DIRECT pedestrian flows must be entered directly for each time segment. Use the <Previous Time> and <Next Time> buttons to move between each time segment.

range > 0.0

7.22 Accident prediction for standard roundabouts This window is used to enter the required data if accident prediction has been specified in “Principal Options” for a standard roundabout (see section 7.23 for accident prediction at mini-roundabouts). The window consists of three frames, entitled “Options”, “Flows” and “Geometry”, (see figure 7-30). The second and third frames are accessed via the <Next...> button. The data required for the model is detailed in sub-sections 7.22.1 – 7.22.3 (pages 130 - 133). For details of how to carry out the necessary measurements see Appendix G, page 233.

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7.22.1 Accident Data (“Options”)

Available Flow data: Specify in this frame what flow information is available for the accident predictions (see figure 7-27). The flow data is entered in the second/following frame.

Figure 7-27 Accident Data (Options) i) Entry Flows only... (minimum requirement). If only entry flows are specified the program will use default turning proportions to estimate exit and circulating flows. To specify additional information/flows the following options are available: ii) Exit flows If exit flows are available and circulating flows are NOT available, the program requires entry flows and exit flows for ALL arms. It will use a Furness balancing technique to estimate circulating flows.

Y/N iii) Circulating flows The program will request entry, exit, and circulating flows. Data need not be entered for all arms - The program will derive accident frequencies/indices just for those arms for which data has been supplied. For the arms with circulating flows data, the corresponding exit and entry data is also needed.

Y/N

Data Input Page 131

Traffic count factors: To estimate AADT flows, traffic flow totals for each vehicle type, are required for a 16 hour period (0600-2200) or a 12 hour period (0700-1900). Select one of the two options. Also specify the site type according to COBA9 (Urban, Inter-Urban or Recreational/Inter-Urban). Urban sites are typically on main roads in urban areas but also include radial routes close to conurbations and important commuting links. Flows do not generally vary from season to season. Inter-Urban sites have summer traffic flows up to 25 per cent greater than average. They are typically on inter-urban roads connecting main centres of population but may also include urban roads at holiday resorts. Recreational/Inter-Urban sites have summer traffic flows at least 25 % greater than average. They are typically inter-urban roads in holiday areas. The site type determines the scaling factor used to derive annual average daily total flows (see COBA9). To enter the AADT flows directly, select the 24-Hour (AADT) option. The traffic collection month is not required, and is set automatically to “AADT”. Traffic collection month (estimated AADT only): Traffic flow data must be collected on a Monday, Tuesday, Wednesday or Thursday (but not a Public Holiday) during April, May, June, August, September or October. Select the month in which the flows were collected. Central Island Diameter (m): Enter the diameter of the central island. In the case of non-circular islands, the maximum value should be given.

range > 4.0

7.22.2 Traffic Flow Data (“Flows”)

This frame is the second of three frames in the accident window and is accessed by clicking on the <Next...> button (see figure 7-28). The accident prediction routines use an annual average daily total flow (AADT) either entered directly or estimated from either 12 or 16 hour counts. The estimation method makes use of appropriate scaling factors (see section 7.22.1, page 131).

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Entry Flow (total traffic): Enter the flow of traffic (including all two-wheelers) entering the roundabout on the arm in question, in thousands of vehicles, during the period specified in the “options” frame (12 or 16 hour).

Figure 7-28 Accident Data (Flows) Entry Flow (motorcycles): Enter the flow of motorcycles entering the roundabout on the arm in question. Exit Flow (total traffic / motorcycles): Enter the flows leaving the roundabout on the arm in question. Requested only if specified in the previous frame. Circulating Flow (total traffic / motorcycles): Enter the flows circulating past the arm in question. Requested only if specified in the previous frame. Pedestrian Flow: Enter the two-way pedestrian flow crossing the arm in question, within 20m along which the entry width is measured. The existence or otherwise of a zebra crossing is irrelevant in this context. All pedestrians should be counted together, whether or not they are using a crossing.

If entry, exit and circulating flow data is available for some arms only, the program will derive accident frequencies/indices just for those arms. Accident frequencies cannot be calculated for arms which have partial data.

Data Input Page 133

7.22.3 Geometric Data (“Geometry”)

This frame is the last of three frames in the accident window and is accessed by clicking on the <Next...> button (see figure 7-29).

Figure 7-29 Accident Data (Geometric) Entry path curvature (1/m): Enter the entry path curvature for each arm.

range -0.01 to+0.05

Approach curvature (1/m): Enter the approach curvature for each arm.

range -0.025 to +0.033

Angle between arms (degrees): Enter the angle between the current arm and the next arm clockwise.

range 40 to 150 Yellow bars on approach: Specify whether there are painted yellow bars across the approach for each arm (if so, ARCADY will assume a 50 percent lower accident frequency).

7.23 Simple Accident prediction for mini-roundabouts This window is used to enter the required data if accident prediction has been specified in “Principal Options” for a Mini-roundabout (see section 7.22 for accident prediction at standard roundabouts). The window is used to enter data for both simple (Model M0) and full (Model M2) accident prediction models. If simple accident prediction has been

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specified in Principal Options this is the only window that needs to be used. If full accident prediction is required, another window, called Full Accident Analysis is needed to enter the additional data required for the more comprehensive accident analysis (see section 7.24, page 136). The window consists of just one frame (see figure 7-28). For details of how to carry out the necessary measurements see Appendix G, page 233. The accident prediction routines use an annual average daily total flow (AADT) either entered directly or estimated from either 12 or 16 hour counts. The estimation method makes use of appropriate scaling factors (see section 7.22.1, page 131).

For the simple ‘M0’ Model provide: Flows by origin-destination (veh x 1000): Enter the flow of traffic by origin-destination in thousands of vehicles, during the period specified in the traffic count factors frame (AADT, 12 hour or 16 hour). (See figure 7-30.)

Figure 7-30 Simple Accident flow data (mini-roundabout) For the full ‘M2’ Model provide: Flows by origin-destination and vehicle type (veh x 1000): Enter origin-destination flows, in thousands of vehicles, during the period specified in the “options” frame (12 or 16 hour). Use the <next> and <previous> buttons to change arms. See figure 7-31.

Data Input Page 135

Figure 7-31 Full Accident flow data (mini-roundabout)

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7.24 Full Accident prediction for mini-roundabouts This window is used to enter the additional data required if Full Accident Prediction has been chosen in “Principal Options”. The window consists of three frames, entitled “Geometry”, “Layout” and “Arm”. (see Figures 7-32 to 7-37). The frames are accessed via the <Next…> button. Each of the frames are described in the following sub-sections. For details of how to carry out the necessary measurements see Appendix G, page 233. The model requires different data for three and four-arm roundabouts.

Any mention of the phrase “from X m“ or “at X m” in this chapter can be expanded to say “X metres back from where the give-way line meets the centre road marking or hatching/island.”

7.24.1 Geometric Data (“Geometry”)

If a 3-Arm mini-roundabout provide: (see Figure 7-32)

Figure 7-32 3-Arm mini-roundabout geometric data (“Geometry”) Minimum exit width (m): For each approach enter the minimum exit width (in metres) measured within 50 metres of the junction (e.g. opposite a refuge).

range 1.8 to 7.0

Data Input Page 137

Entry width along give-way (m): For each approach enter the entry width in metres. If a left-turn splitter island exists include it and also the entry width on both sides of it.

range 2.0 to 20.0 Angle between Arm n and Arm (n+1): For each approach enter the angle between it and the next approach (clockwise) in degrees.

range 0.0 to 200.0 Gradient from 50-100m on approach (%): For each approach enter the average gradient for the 50-100 metres from the junction (in degrees).

range –15.0 to 15.0

If a 4-arm mini-roundabout provide: (see Figure 7-33) Minimum exit width (m): For each approach enter the minimum exit width (in metres) prior to any flare and within 50 metres of the junction (e.g. opposite a refuge).

range 1.8 to 7.0 Effective Flare length (m): If there is no flare the flare length should be set to zero. (Measured in the same way as the geometric data effective flare length of a standard roundabout.)

range 0.0 to 45.0

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Figure 7-33 4-Arm mini-roundabout geometric data (“Geometry”)

Min. distance from junction centre to projected arm centre line (m): If the projected arm centre line is to the right of the junction centre a negative value should be entered.

range -4.0 to 10.0 Min. distance from junction centre to entry corner kerbline (m):

range 4.0 to 22.0 Distance from junction centre to offside end of give-way line (m):

range 3.0 to 17.0

7.24.2 Geometric Data (“Layout”)

If a 3-Arm mini-roundabout provide: (see Figure 7-34) Number of entry lanes: For each approach enter the number of lanes on the approach, upstream of any flaring.

range 1 to 2 Number of exit lanes: For each exit enter the number of lanes upstream of any flare (measured at the same point as the number of entry lanes).

range 1 to 2 Number of side roads within 20m on exit side of arm: In the unlikely event of there being more than one side road, enter 1.

range 0 to 1 Sight distance to right from 4m (m): Enter the sight distance observed at 4 metres back from where the give-way line meets the centre road marking or hatching/island. The target, on the nearside of the previous arm, should be observed from the centre of the arm. The measurement should be recorded from the ‘datum’ point D(n-1) (see Appendix G, page 233).

range 0.0 to 300.0 Sight distance to right from 50m (m): Enter the sight distance observed at 50 metres back from where the give-way line meets the centre road marking or hatching/island.

range 0.0 to 300.0

Data Input Page 139

Figure 7-34 3-Arm mini-roundabout angles and sight distances (“Layout”) If a 4-arm mini-roundabout provide: (see Figure 7-35) Angle between arm n and arm (n+1): Enter the angle between the current arm and the next arm clockwise, measured between the tangents to the centre lines at 20 metres, in degrees. Take account of islands if there are any.

range 0.0 to 180.0

Figure 7-35 4-Arm mini-roundabout angles and sight distances (“Layout”)

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Angle between arm n and arm (n+1): Enter the angle between the current arm and the next arm clockwise, measured between the tangents to the centre lines at 0 metres, in degrees.

range 0.0 to 180.0

Sight distance ahead from 0m: Enter the sight distance ahead observed at 0 metres back from where the give-way line meets the centre road marking or hatching/island. The target, on the nearside kerb of the arm opposite, should be observed from the centre of the arm.

range 0.0 to 300.0 Sight distance to right from 4m: Enter the sight distance ahead observed at 4 metres back from where the give-way line meets the centre road marking or hatching/island. The target, on the nearside kerb, should be observed from the centre of the arm. (see Appendix G, page 233).

range 0.0 to 300.0 Sight distance to right from 50m: Enter the sight distance ahead observed at 50 metres back from where the give-way line meets the centre road marking or hatching/island.

range 0.0 to 300.0 7.24.3 Geometric Data (“Arm”)

If a 3-arm mini-roundabout provide: (see Figure 7-36) Shops within 20m of entry or exit of next arm: Indicate whether the dominant land use is shops or shops/residential. (For these purposes ‘shops’ include banks but exclude cinemas and restaurants.)

Y/N

Major junction within 200m: Indicate the presence of a major junction is within 200 metres. A major junction is any junction at which traffic leaving the current arm has to give-way, or is stopped, or could be stopped, i.e. any junction excluding side roads, but including level crossings.

Y/N Single yellow / double yellow / zigzag markings within 20m on exit side:

Y/N

Data Input Page 141

Figure 7-36 3-Arm mini-roundabout junction and arm features (“Arm”) Central island within 20m: Indicate the presence of a central island within 20 metres back from where the give-way line meets the centre road marking or hatching/island..

Y/N Length of island, including hatching (m): Enter the overall length (including hatching) of the island, any part of which is within 20 metres. Include islands at pedestrian crossings.

range 0.0 to 100.0 If a 4-arm mini-roundabout: (see Figure 7-37) Domed central island: (whole junction): Indicate the presence of a domed central island, i.e. domed rather than flat or ‘bumpy’.

Y/N Shopping land use within 20m of junction: (whole junction): Indicate whether the dominant land use within 20 metres of the junction is shops or shops/residential buildings. (Shops includes Banks but excludes cinemas and restaurants.)

Y/N

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Major junction within 200m: Indicate the presence of a major junction is within 200 metres, i.e. a junction at which traffic leaving the current arm has to give-way, or is stopped, or could be stopped, i.e. any junction excluding side roads. Include level crossings.

Y/N

Guard rail on exit side of arm: Indicate the presence of any amount of either guiding or deterring guard railing on the exit side within 20 metres of the junction

Y/N

Presence of entry path curvature on arm: Indicate the presence of entry deflection, taking account of lane markings.

Y/N

Approach curvature within 100m: Indicate the direction of curvature and the degree of curvature.

Left/Straight/right and Slight/moderate/sharp

Figure 7-37 4-Arm mini-roundabout junction and arm features (“Arm”)

Output and its interpretation Page 143

8 The Output and its Interpretation 8.1 About this chapter This chapter describes the analysis output of ARCADY. Since most of the output is self explanatory, this chapter is mainly intended as a reference and guide to interpretation. Nevertheless new users may benefit from reading this chapter to clarify what information is available and the form it is presented in. Users of previous versions of ARCADY should read this chapter because the ARCADY 6 output analysis is now presented in an entirely new way. Previous versions of ARCADY presented the output in the form of an ASCII text file. ARCADY 6 still does this but additionally it has a powerful Report Designer facility (See Section 6.12, page 61) which creates a user-designed report with extra output if requested. Because all the output within the ASCII file can be included in the report, this chapter focuses on describing the output that is in the report rather than the ASCII file. Another reason for this is that it is also likely to be most users’ preferred method of viewing, printing and presenting results due to the added functionality, clarity, and flexibility that it provides. It is also TRL’s recommended method. Viewing of the report via the Report Viewer is described in section 6.13, page 71.

ARCADY 6 still provides ARCADY’s ‘original’ ASCII output which can be viewed and printed using the TRL VIEWER program. Viewing ASCII text files is described in section 6.15, page 78.

8.2 Characteristics of the output/Output overview The report is created in two formats; .VAR – which can only be viewed via the Report Viewer Standard View and .HTM – (i.e. HTML) which can be viewed via the Report Viewer HTML View and in Internet Explorer.

Images used in the HTML file are saved in the same directory as the actual HTML file. Therefore, to move the file, for example to email it to a colleague the images associated with that file must be moved as well.

The HTML format report may also be cut and pasted into

Microsoft Word to create one single document with all the images embedded. It has been found that sometimes if a cut-and-paste operation is attempted on the HTML file in one go, errors may occur during the paste

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operation. If this happens, copying and pasting smaller sections of the HTML file will probably be successful.

8.3 Output to the screen The ARCADY analysis program produces no output to the screen during the analysis of a junction except for warning and error messages (if any). If the report has been run via the Report Designer (see section 6.12 page 61), on completion of the analysis the Report Viewer (see section 6.13 page 71) will open with the new report displayed. If not, the report (if one exists) can be viewed using the Preview button on the main toolbar or by using View/Report on the main menu. (The ASCII output file can be viewed using View/Output File.) 8.4 Junction assessment data – capacity, queues and delays

This section describes each item that may be included in the report. It follows the order in which items may appear in the Report Designer’s ‘Items’ frame (see section 6.12 page 61). However, it should be remembered that the order that the items appear in the actual report is defined by the user. Banner (mandatory)

Figure 8-1 Banner The banner (which is always included in the report) shows information about the program release date and version number (which may vary, but will be required if you need help or advice). Note the important statement at the bottom of the table which warns all users to be aware that ARCADY is a modelling tool and like all tools, it is possible to use it badly. It is very much up to individual users to ensure that any solution found is a good solution.


Run Information (mandatory)

Figure 8-2 Run Information Information regarding the location of the file, what time it was run, whether it was run in drive-on-the-left or drive-on-the-right mode, and what units were used is always included after the banner in the report. Arm Labelling (mandatory)

Figure 8-3 Arm Labelling

Each approach of a junction may be given an optional label to identify it in terms of road name for example. The output still refers to the approaches as arms A to G, thus this table can be used as a reference. Flow Scaling Factor (mandatory)

Figure 8-4 Flow scaling factors

For each arm of a junction the specified demand flows (specified elsewhere) can be scaled. The default of 100% will leave the values as they are - 200% will double them.

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File Properties

Figure 8-5 File Properties

Presents all the information from the Run Information screen. Errors and warnings

Figure 8-6 Errors and Warnings Any errors or warnings are reported here. The messages are largely self-explanatory. The warnings are given in situations considered to be unusual in some respect. The errors and warning reported here are also displayed on the screen as soon as they occur during the run of the analysis program. Where warnings are made, it is recommended that the data is checked to ensure the model has been specified as intended and that no mistakes have been made. Errors on the other hand are more serious and will cause the program to terminate. Examples of some of the sorts of errors that may appear are shown in section 6.21, page 91. 8.4.1 Listing of input data

The purpose of listing the input is to provide a record of the user-supplied input data in order that it can be checked. The listing consists of a series of tables, of the following form:


Geometric Data

Figure 8-7 Geometric Data

This table contains the geometric data related to capacity calculations and values of the intercept and slope (calculated by the program) for each arm of the junction.

Some other output may also appear depending on the input data as shown below.

Geometric Delay Data

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Figure 8-8 Geometric Delay Data

Three tables are produced when the assessment of geometric delay has been selected. The tables contain the geometric delay data, including junction geometry, distances travelled through the junction, and speeds. Site-specific observations and adjustment

Figure 8-9 Site-specific observations and adjustment

This table is produced when site-specific observations, related to capacity corrections, are present. The intercept adjustment shown can be either positive or negative as it represents the change in the intercept with the y-axis of the graph of entry capacity against circulating flow (which is a linear relationship). The same adjustment is applied to the entry capacity for all values of circulating flow. The example table shows a site-specific adjustment has been made to all arms. On arm B the mean entry flow is 20 PCU/min and mean circulating flow of 20.1 has been observed on site, resulting in an adjustment to the intercept of the capacity relationship for this arm of -3.137 PCU/min. This means that the capacity of this arm is slightly less than the program would normally predict.


Junction Diagram

Figure 8-10 Junction Diagram

The junction schematic can be small, medium or large. The image shown depends on the Junction Diagram options specified prior to the report being generated. E.g. the diagram shown (Figure 8-10) shows the queues at 07:15. Junction Image The roundabout image is set in the ‘Junction Type’ screen.

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Demand Data

Figure 8-11 Demand Data

The table in figure 8-11 contains any demand data (unless the DIRECT demand option was selected, when demand flows appear in the ‘output’ tables only). Traffic demand data is required for the period being analysed. An example of data, which was entered using the LEVELS option, is tabulated above. The table will vary depending on the demand option used. When multiple demand sets are specified the data for each set is produced in a separate table.

When using the ODTAB option the peak hour demand flows specified on input will not be those that appear as total demand flow per hour in the summary tables. This is because the summary tables present average flows over the whole period modelled, i.e. 90 minutes in this case, which includes 30 minutes of off-peak flows in addition to the peak hour.

No flow tables are produced for DIRECT data in the report or the ASCII text file. Also included in Demand Data is the vehicle and turning proportions.

Figure 8-12 Heavy Vehicle Proportions


The table in figure 8-12 gives the heavy vehicle proportions (which may be default or those specified by the user). The size of the table can vary depending on, for example, whether proportions vary over time. When multiple demand sets are specified the data for each set is produced in a separate table.

This table or similar – (see above text) is created by ARCADY for all ‘Heavy Vehicles” Principal Option settings.

Figure 8-13 Turning Proportions

The table in figure 8-13 shows the turning proportions used (which may be default or those specified by the user). If the turning proportions shown are derived from turning counts, the counts they are calculated from are also shown (in shaded text).

This table is created when turning proportions are entered in LEVELS or FOUR options or in some cases when using the DIRECT option.

Demand Data Graphs

Direct Levels Four

Chapter 8

These graphically illustrate the flow entered in Demand Data. The graph drawn differs depending on the Demand Data type. The above pictures indicate the different types of graphs created for the various demand types. Graphs are drawn for each demand set. If the DIRECT option is being used they may be plotted as all arms on one graph or as individual graphs for each arm, and the graph can drawn in either continuous or stepped mode, as described in section 6.12.4.3 and 6.12.4.4.

There are no graphs when the ODTAB option is used.


Crossing Data

Figure 8-14 Crossing Data

The pedestrian flow on a crossing may be high, and, if so, dominate the junction entry capacity. Furthermore, pedestrian flows at a crossing may restrict traffic leaving the junction and cause blocking back to the junction entry of an upstream arm. This blocking back may become so serious that the whole junction could lock up. In such extreme circumstances, indicated (for Zebra Crossings only) in the printed output, the capacity formulae are inappropriate because drivers will try to compensate for the lack of capacity. The presence in the output of several of the warning messages (see section 8.6, page 173) relating to the presence of a zebra crossing on the performance of the roundabout would indicate an unsatisfactory junction design. The Pelican crossing model does not currently model this situation (i.e. blocking back) hence no warning in the output is currently possible.

Chapter 8

8.4.2 Listing of output results

For the “fully saturated” option the results are printed in one table that shows the capacities of each arm and the entire roundabout under fully saturated conditions.

Otherwise, the output pages consist of the following items, some of which are dependent on the options selected by the user: Queues and Delays

Figure 8-15 Queues and Delays Tables of demand flows, capacities, queues, delays and (if selected) geometric delays, for each time segment are produced. These contain start and finish times and, for each arm, traffic demand, capacity, ratio of flow to capacity (RFC), start queue-length, end queue-length and queuing delay. The RFC provides a basis for judging the acceptability of junction designs, as described in Departmental Advice Note TA23. It must be stressed that the calculated queues and queuing delays are average values of broad distributions, and considerable variation about these values will be encountered in practice. In fact, day-to-day variations in the queue-lengths and delays can occur at any given time in the peak period.


These average values may be checked only by making careful and detailed observations on many days. Use of the queue variability option (Section 4.2, page 17) will show the day-to-day variability of queues on each arm in each time segment, and will indicate, implicitly, the number of days observations required to obtain reliable average queues. The queuing delays are given for each time segment in vehicle-minutes. This means the delay suffered during that time interval by all the vehicles which are queuing during that time.

It is not possible to derive the average delay per arriving vehicle by simply dividing this figure by the demand flow in that segment, because vehicles arriving in one time segment may also suffer delay in other time segments.

An important improvement in ARCADY is that, unlike previous versions, ARCADY 6 produces an estimate of delay (in minutes) per arriving vehicle on a given arm by taking into account the changing situation from segment to segment.

The time-consuming manual calculations needed to produce approximate values of delay per arriving vehicle, which could be inaccurate when vehicles were queuing for longer than one time segment, are no longer needed.

Overall Queues and Delays

Figure 8-16 Overall Queues and Delays This summary table, giving the overall queuing delays for the entire simulation period, is produced for all runs of ARCADY.

Chapter 8

The contents are: arm identifier, total demand, delay and inclusive delay. The table also shows overall totals for demand, delay and inclusive delay for the whole junction. The difference between “delay” and “inclusive delay” has been explained in section 5.3, page 40. Geometric Delay

Figure 8-17 Geometric Delay

This information is produced only when the assessment of geometric delay has been selected. The summary table gives the total geometric delay experienced by all vehicles making each turning movement, the overall total geometric delay (vehicle minutes) and the mean geometric delay per light vehicle (seconds). The geometric delays calculated are the totals for all vehicles making a particular turning movement during the period being modelled. Since vehicle flows during the modelled period are unlikely to be representative of the whole day (the modelled period is usually a peak) it follows that it is not possible to obtain accurate total daily geometric delays by simply factoring up the values output by the program - total geometric delays per unit time will vary throughout the day.

Geometric delays calculated for asymmetric roundabouts are subject to some error due to the fact that, for some movements, the “no-junction” journey time will not be accurately defined by specifying a single point as the centre of the junction. If point-to-point delay calculations have been requested, ARCADY produces an additional table of point-to-point journey times. The entry in each cell of the table is the average journey time (over the whole modelled period) per PCU in seconds from the


indicated origin to the indicated destination. This journey time is made up of the travelling time (the time taken to travel along the approach to the roundabout, round the circulating carriageway to the exit arm, and then along the exit arm) together with any queuing delay at the roundabout entry. Marginal Analysis (Capacity) This table is produced when “Marginal Analysis” has been requested. It contains the estimated effects of small changes in flows or junction geometry on capacity. In particular, extensive marginal analysis is carried out on mini-roundabouts.

Figure 8-18 Marginal Analysis

Chapter 8

Queue diagrams A set of diagrams can be created and included in the report (one for each time segment) or alternatively, just one diagram of the segment with the largest queue depending on what has been selected in the Report Designer’s Item Options frame. The view extent is selected automatically to include the whole length of any queue. Hence, the longer the queues the smaller the scale of the diagram. The diagram may be one of three sizes as set in the Report Designer’s Formatting Options using ‘Other Diagram Size’.

Figure 8-19 Queue diagrams (medium size)


If queue variability is chosen, the queue diagrams additionally show the key points of the frequency distribution of queues, i.e. 5th percentile, mean (surrounded by a thin black line), 90th percentile and 95th percentile queue-lengths. Different shading is used to show the different values. The darkest shade is used for the 5th percentile and the lightest for the 95th. Capacity Graph

Figure 8-20 Capacity Graph

In this example the capacity graphs show a typical trough shape reflecting the fact that the circulating flows past each arm increase during the peak of the demand flows specified. RFC Graph

Figure 8-21 RFC Graph

Chapter 8

The ratio of flow to capacity (RFC) graphs indicate how near each approach is to maximum capacity. Any value over 1 will indicate that the entry is overloaded and queues will continue to increase for as long as this situation continues. However, users will be aiming for a lower value to allow for the randomness of arrivals. Start/End Queue Graphs

Figure 8-22 Start Queue Graphs

Tables showing the profile of queues over time can be generated for all runs of ARCADY. Graphs showing the queue at the start of each time interval (see figure 8-22) or the queue at the end of each time segment (see figure 8-23) can be selected. N.B. the two graphs will look very similar as one is simply a lateral shift of one time interval of the other, i.e. one is showing the queue length at the start of the time interval while the other the queue at the end of the same time interval.

Figure 8-23 End Queue Graphs


Figure 8-24 Queue Distribution and Queue Markers

When queue variability is chosen, an additional table shows a tabulated cumulative frequency distribution of queue-lengths over the modelled time period for each arm. If any queue markers are defined, the table also shows the probability that the queue will reach the queue marker on that arm. In this example there is a queue marker on Arm C (positioned 200 metres from the start of the flare). The other three arms do not have queue markers. In extreme cases, such as when very large queues occur towards the end of the modelled period, the analysis is not possible. This is indicated by special symbols on the output, with an explanatory key.

Chapter 8

Figure 8-25 Queue Variability and Queue Graphs

When queue variability is chosen, the start and end queue graphs additionally show, for each arm and each time segment, the key points of the frequency distribution of queues, i.e. 5th percentile, mean, 90th percentile and 95th percentile queue-lengths. Different colours are used to show the different values. These diagrams provide the user with an indication of which arms are likely to have queuing problems and which arms are likely to have minimal queues.

When the mean queue is large there is a large difference between the mean queue and the 95 percentile queue.

This method of displaying the values is also used for the queues shown on the junction schematic.


Geometric Delay Graph

Figure 8-26 Geometric Delay Graph

The geometric delay graphs are a graphical representation of the data that is also provided in the geometric delay table.

Chapter 8

Delay Graph

Figure 8-27 Delay Graph

The delay graphs are a graphical representation of the data that is also provided in the delay table.


8.5 Junction assessment data - accident prediction

This section describes the output for both simple and full accident prediction. The following input and output data is presented in the ARCADY output when the prediction of accident frequencies/indices is specified by the user. The predicted accident frequencies/indices are tabulated by arm and classified by vehicle, pedestrian and accident types. The results are expressed as indices, which increase with accident frequency, where 1.0 corresponds to the frequency of accidents for the junctions studied in LR 1120 (Maycock and Hall 1984). Accident frequencies are also given if the junction is of the type studied in LR 1120 (i.e. four-arm at-grade roundabouts), and its geometric parameters fall within the range over which the model was calibrated (see section 4.4, page 19). If the junction is a mini-roundabout accident frequencies are also given. The accident indices output are such that junctions (or arms of junctions) with accident indices less than 1.0 have a lower predicted accident frequency than the average of the measured results in LR 1120. Those with an index over 1.0 have a higher predicted frequency. It should be remembered that higher than average flows will increase this index, even for a well designed approach/roundabout. The indices should be interpreted only as giving an indication of the relative safety of arms, or junctions, when any pair are compared.

If the junction is a circular four-arm at-grade roundabout the program will also output the personal injury accident frequencies per year, unless any of the geometric parameters are outside the acceptable range (in which case indices only are given).

If “Marginal Analysis” has been requested (Section 4.8, page 24) additional tables giving the estimated effects of small changes in flows or junction geometry on accident frequencies/indices. In particular, extensive marginal analysis is carried out on mini-roundabouts. 8.5.1 Listing of input data

The data required for accident prediction depends on whether the junction is a standard roundabout or mini-roundabout and on whether simple or full accident prediction is chosen. Full accident prediction is only available for mini-roundabouts. One of each of the possible tables showing the accident input data is shown below. Any necessary explanations appear below the relevant tables.

Chapter 8

Figure 8-28 Input data for simple model (standard roundabout)

Figure 8-29 Flows for simple model (standard roundabout)


Figure 8-30 Input data for simple model (mini-roundabout)

Figure 8-31 Flows for full model (mini-roundabout)

In this example the accident flow data has been entered as PCU values instead of using the six vehicle types, hence the reason for all the flows having been entered as cars/light goods vehicles – they have a PCU value of 1.

Chapter 8

Figure 8-32 Junction Geometry and Layout for full model

(mini-roundabout)


8.5.2 Listing of output results

Figure 8-33 Vehicle and Pedestrian Injury Accidents using simple model (standard

roundabout) For large or grade-separated roundabouts only accident indices (not frequencies) are calculated.

Figure 8-34 Vehicle and Pedestrian Injury Accidents using simple or full model

(mini-roundabout)

Chapter 8

Marginal Analysis (Accident)

Figure 8-35 Marginal Analysis (Pedestrians)

(standard roundabout) In this example the warning message appears because the flow data relating to accident prediction was specified in the form of an entry flow profile and exit flow profile, which are not exactly the same, so the total entry flow and exit flow in any particular time segment will not be exactly the same.


Figure 8-36 Marginal Analysis using simple or full model

(mini-roundabout) These tables are generated when a mini-roundabout is being modelled using the full (M2) accident model and marginal analysis has been specified. It shows the predicted effects on capacity of small discrete changes in traffic flows, pedestrian flows and junction geometry. The results in the first table appear in the form of a grid because the

Chapter 8

marginal changes in the variables listed affect the accident predictions on more than one arm of the roundabout. A space containing a “-” indicates that a variable does not affect that particular arm. The fist table shown is that of a four-arm roundabout – a similar, but different, table is generated for three-arm roundabouts. This table clearly shows for example how changes in the “minimum distance from junction centre to projected arm centre line” on one arm affects the accident frequency on the next arm clockwise.

The second table shows a set of variables for which changes affect only the arm on which the change has been made. In the example shown, an increase in pedestrian flow on Arm C by +10% would see an increase of +0.002 in the accident frequency on Arm C, but no change on any other arm.


8.6 Error messages 8.6.1 Data errors and warnings

The analysis program outputs a variety of error and warning messages, some of which are discussed in more detail below. Some of the error messages relate to range checks on the input data. Where an input value falls outside the valid range for that parameter a self-explanatory FATAL or WARNING message is printed. The graphical user interface is specifically designed to avoid many of the possible range errors, therefore it should be used to make all changes to data files. It should be noted, in particular, that if any of the input geometric parameters lie outside the range over which the capacity formulae were developed, the following message is printed: * WARNING * ARM x - INPUT VALUE OF y (n.nn) WAS OUTSIDE ACCEPTABLE RANGE - IT HAS BEEN RESET AS INDICATED ABOVE (*). The incorrect value is replaced with one that is within the acceptable range, which is indicated with an asterisk.

8.6.2 Model warnings

The following warnings are given when the program detects that modelled conditions at a junction are abnormal. i) A warning message is printed if the entry capacity of any traffic stream becomes

zero during the modelled period. By implication the user has a junction which is probably unworkable: the value for delay may have exceeded the output format. The message is:

* WARNING * THE ENTRY CAPACITY OF AT LEAST ONE ARM HAS BECOME ZERO DURING THE PERIOD MODELLED.

If demand flows are correct, the only solution is to alter the junction layout.

ii) A warning message is printed when non-convergence in the calculation of entry

flows for a particular time segment has occurred. If by a combination of exceptional circumstances convergence is not achieved for one or more arms the following message is printed:

Chapter 8

* WARNING * ENTRY FLOWS IN CERTAIN TIME SEGMENTS (FLAGGED ++ IN THE TABULATION) DO NOT STABILISE WITHIN THE ALLOCATED NUMBER OF ITERATIONS AND HENCE THESE RESULTS ARE UNRELIABLE Non-convergence usually occurs when opposing pairs of arms of a four-arm junction having identical entry capacity relationships and demand flows. Introducing a very small element of asymmetry into the layout can eliminate this. Alternatively, if non-convergence occurs while using the LEVELS demand option, convergence may be achieved by changing t1, t2 and t3 by a small part of the time segment length (t1, t2 and t3 do not need to be multiples of the time segment length) while leaving the total modelled period (t4 ) unchanged.

iii) Where pedestrian crossings are modelled, a warning message is given if the

junction entry capacity on any arm is greater than the capacity of the crossing on that arm. This is usually the result of high pedestrian flows. In such circumstances the crossing totally dominates the junction entry, and the following message is printed:

*WARNING* ENTRY CAPACITIES IN CERTAIN TIME SEGMENTS (FLAGGED XX IN THE TABULATION) ARE DOMINATED BY THE PEDESTRIAN CROSSING.

This probably indicates unsatisfactory operation of the junction, and measures such as segregation of pedestrian traffic may be appropriate.

iv) A warning message is given when traffic leaving the junction is likely to queue

back from a pedestrian crossing, across the upstream junction entry for more than 10 per cent of the time segment. The affected arm is flagged in the main tabulation and the following message is given:

* WARNING * ENTRY CAPACITIES IN CERTAIN TIME SEGMENTS (FLAGGED BB IN THE TABULATION) ARE RESTRICTED DUE TO TRAFFIC QUEUING TO LEAVE THE JUNCTION ON AN ADJACENT ARM.

If this blocking back increases to more than 90 per cent of the time, it is likely that the whole junction will lock due to traffic blocking entries. In such circumstances the capacity formulae for the junction may be inappropriate and the following warning is given:


* WARNING * JUNCTION LIABLE TO SUDDEN COMPLETE BLOCKING IN CERTAIN TIME SEGMENTS (FLAGGED LL IN THE TABULATION) DUE TO TRAFFIC AT A CROSSING BEING UNABLE TO LEAVE THE JUNCTION.

The flagging of several arms or time segments in this way indicates that the junction will probably not operate satisfactorily, and that measures such as the segregation of pedestrian traffic may be appropriate.

v) A warning message is printed if geometric delays are calculated and the

roundabout is either non-circular or non-symmetrical. There is a need for caution due to the use of a single point to define the centre of the roundabout. The distances from the entry to this centre, and from this centre to the exit, may not be the most suitable measurements for calculating the geometric delay associated with some of the turning movements when the roundabout is asymmetric. The message is:

* WARNING * GEOMETRIC DELAYS HAVE BEEN CALCULATED AND THE ROUNDABOUT IS NON-CIRCULAR OR NON-SYMMETRICAL.

vi) A warning message is given when geometric delay is being calculated and an

approach-speed or departure-speed is lower than the calculated within-junction speed. This implies a negative component for geometric delay and may suggest an error in the input value of speed. The message is:

* WARNING * IN THE CALCULATION OF GEOMETRIC DELAYS THE APPROACH/DEPARTURE SPEED ON ARM X IS LESS THAN THE CALCULATED JUNCTION SPEED

vii) A warning message is given if accident predictions are to be made and the

roundabout is non-circular. Only accident indices can be calculated. The message is:

* WARNING * THE ROUNDABOUT IS NON-CIRCULAR SO ACCIDENT FREQUENCIES CANNOT BE CALCULATED.

viii) A warning message is given if the traffic flows specified by the user are

inconsistent. It is natural for measured ‘real’ flows, in and out of the junction, to be marginally inconsistent. This message is intended to remind users to check their data for any major inconsistencies. The message is:

* WARNING * THE TOTAL TRAFFIC ENTERING THE JUNCTION DOES NOT EQUAL THE TOTAL TRAFFIC LEAVING .

Chapter 8

ix) For a standard roundabout a warning message is given if any of the flare lengths specified by the user are outside the range over which the capacity formulae were developed (i.e. 30 metres). Although the program will use the flare length given, the calculated capacities should be treated with increasing caution. The message is:

* WARNING * ARM x - EFFECTIVE FLARE LENGTH IS OUTSIDE NORMAL RANGE – TREAT CAPACITIES WITH INCREASING CAUTION.

x) A warning message is output when geometric delay is being calculated and the program-calculated distance required to allow for accelerations and decelerations is longer than the user-defined distance over which the point-to-point journey time is measured. The message is: * WARNING * ACCELERATION DISTANCE EXCEEDS CALCULATION DISTANCE ON AT LEAST ONE ARM.


8.7 Examples A number of fictitious examples of roundabouts have been constructed that illustrate most of the junction analysis features available within ARCADY. Both data files and output results files are supplied with the ARCADY product so that the files can be run and the results compared with those supplied.

The examples do not relate to real junctions, and it is not implied that a junction could be constructed based on the data supplied.

At the time of writing the files supplied are as follows:

1. Example 1 is a conventional at-grade roundabout, with zebra crossings on Arms B and C. Vehicular demand flows are specified using the LEVELS method. Marginal analysis is specified.

2. Example 2 is a the same as Example 1 except that queue variations are

specified.

3. Example 3 is a large grade-separated roundabout. As it is of this type, only accident indices are output, not accident frequencies as in the previous example. A site-specific capacity correction is applied to Arm D. A mean entry flow of 13.2 pcu/min. and a mean circulating flow of 21.7 pcu/min. has been observed on site, resulting in an adjustment to the intercept of the capacity relationship for this arm of -13.05 pcu/min. (This means that the capacity of this arm is significantly less than the program would normally predict - the normal intercept is 34.962 pcu/min. Queue-markers are specified for Arms B and D. Queue distribution analysis is shown since queue variability is specified. The queue distribution diagrams show typically large daily queue variability at the height of the peak on the congested arms.

4. Example 4 is a 3-arm mini-roundabout with Pelican crossing on Arm C.

Vehicular demand flows are specified using the DIRECT method. The effect of the pelican crossing on the queues on arm B can be seen clearly in time segments 08:00-08:15 and 08:15-08:30.

5. Example 5 is a 4-arm mini-roundabout with no crossings. Note that the

vehicular demand flows are specified using the FOUR method. Full Accident prediction is specified.

The accident flow data have been entered as PCU values instead of the six vehicle types, hence the reason for all of the flows having been entered as cars/light goods vehicles – they have a PCU value of 1.

Chapter 8

Marginal analysis is specified hence both geometric and accident marginal analysis tables have been generated. As with all ARCADY output results, the queue and delay results for each time segment as well as for the whole modelled period are produced.

8.8 ASCII (.VAO) output results file Although the whole of the output results are presented in the ARCADY Report, users may wish to still look at and refer to the ‘classic’ ASCII (*.VAO) output files. For those using VAO files the following points should be noted:

• In the queue histogram, showing the development of queues on each arm through time, each asterisk represents one vehicle up to a maximum of 90. If the mean queue-length exceeds this value, its actual value is still printed alongside.

• If queue distributions have been requested, the histogram shows a single asterisk to represent the last vehicle in the mean queue, and other symbols to represent the last vehicle in the 5 percentile, 90th percentile and 95th percentile queues.

• The following symbols are used:

“:” for the mean value (50th percentile) “+” for the 95th percentile “*” for the 90th percentile “-” for the 5th percentile

There is a hierarchy of symbols applied when two or more occur at the same point - only the highest priority symbol will be printed. The hierarchy is:- Mean, 95th percentile, 5th percentile, 90th percentile.

• In extreme cases, such as when very large queues occur towards the end of the

modelled period, the analysis is not possible. This is indicated by special symbols on the output, with an explanatory key.

Modelling Special Situations Page 179

9 Modelling Special Situations 9.1 About this chapter This chapter describes certain special situations and how to deal with them. Any modelling restrictions that apply to these situations are also given. 9.2 Entry-only and exit-only arms There may be some entry-only or exit-only arms at the roundabout, for example in a one-way system. An entry-only arm should be treated as an ordinary arm. It is worth noting that since there will be no traffic leaving the roundabout at this arm, the specification of turning proportions will reflect this fact. The use of default turning proportions is therefore prohibited. Also, in this case the entry width, e, is the entire width of the road. Similarly v is the total approach road width. Any exit-only arm should be included in the total number of arms at the roundabout, and identified in the Junction Type window (section 7.6, page 97). The checking of input data and printing of results are revised to take account of exit-only arms. Exit-only arms cannot be specified for mini-roundabouts 9.3 Motorway-type slip roads Roundabouts having arms which are slip-roads to and from a motorway or dual-carriageway should be modelled in the normal way, i.e. a pair of slip-roads should not be considered as one entry-only arm and exit-only arm, but as the entry and exit of a single arm. For example, a roundabout at a grade-separated interchange where a motorway crosses an all-purpose road would be modelled as having four arms rather than as having six arms with two entry-only and two exit-only arms. 9.4 The treatment of filter lanes A filter lane, in this context, is a lane carrying left-turning traffic which does not have to give way to circulating traffic at the give-way line. Instead, the left-turners proceed virtually unhindered, and usually merge with other traffic some significant distance from the roundabout. The presence of a filter lane can be allowed for as follows. For each arm with a filter lane, measure the widths v and e from the centre of the road to the offside edge of the filter lane, i.e. the usual measurements but excluding the width of the filter lane. Measure the entry radius, r, to the offside of the filter lane and conflict (entry) angle, φ, for the traffic not using the filter lane. The demand flow for the approach is specified excluding the filter lane flow. The roundabout is then modelled by ARCADY for all traffic not using the filter lane(s). The capacity of each filter lane can be taken to be independent of the circulating flow

Chapter 9

and equal to approximately 1000 pcu per hour. Any queuing for the filter lane would not then be included in the ARCADY output. Also not modelled, is the effect of entry starvation caused by a filter lane that is fed by a lane containing traffic not turning left. (Starvation is the effect whereby traffic is unable to reach the give-way line due to being stuck in a queue of traffic wishing to make the other movement.) There could be a significant number of left turners unable to make their exit if the queue (for the other movement(s)) extends past the point where the filter lane starts. 9.5 Double-island roundabouts It should be noted that only single-island roundabouts can be modelled explicitly by the program. Although double roundabouts can, in theory, be treated by modelling each of the component roundabouts separately, this is not recommended because any interaction between the individual components will not have been considered. 9.6 Other special situations When modelling any special situation it is worth looking at the Help tips file provided with ARCADY. Under the section entitled “Frequently Asked Questions” there are a variety of articles (from a variety of sources) concerning the use of ARCADY. It includes suggestions on how to use it beyond its originally defined use.

An alternative (and probably more up-to-date) source for this information is our software web site at www. trlsoftware.co.uk

Acknowledgements and references Page 181

10 Acknowledgements The author is grateful for advice given by Mark Crabtree on a variety of topics, and Janet Kennedy’s advice on the mini-roundabout accident predictions. The work described in this Application Guide forms part of the software development programme of the Transportation Division, TRL Limited.

11 References 1. BINNING, J C (2006). PICADY 5 User Guide, Transport Research Laboratory,

TRL Application Guide AG56. TRL Limited. 2. BINNING, J C (2000). ARCADY 5 User Guide, Transport Research Laboratory,

TRL Application Guide AG36. TRL Limited. 3. BURROW, I J (1986). The effect of darkness on the capacity of road junctions.

Traffic Engineering and Control, 27 (12), pp 596-599. 4. BURROW I J, R M KIMBER, N HOFFMANN and D WILLS (1983). The

prediction of traffic peak shapes from hourly flow counts. Department of the Environment Department of Transport, TRRL Report SR 765. Crowthorne: Transport and Road Research Laboratory.

5. DEPARTMENT OF TRANSPORT (ASSESSMENTS POLICY AND

METHODS DIVISION). COBA9. A method of economic appraisal of highway schemes, 1981.

6. DEPARTMENT FOR TRANSPORT, Design Manual for Roads and Bridges:

Volume 13 - Economic Assessment of Road Schemes. Section 1: The COBA Manual. HMSO, London. (COBA10)


Volume 6, Section 2 - Geometric Design of Major/Minor Priority Junctions. Departmental Standard TD 42/95, 1995.


Volume 12, Section 1 - Traffic Appraisal Manual, 1981.

Chapters 10 and 11


Volume 6, Section 2 - Junctions and accesses; determination of size of roundabouts and major/minor junctions. Departmental Advice Note TA 23/81, 1981


Volume 6, Section 2 - The geometric design of roundabouts. Departmental Standard TD 16/93, 1993

11. GRIFFITHS J D (1979). Mathematical Models for Delays at Pedestrian

Crossings. Bulletin of IMA No.11/12 12. KENNEDY, J V, R D Hall, S R Barnard (1998). Accidents at Urban mini-

roundabouts, Transport Research Laboratory, TRL Report 281. Crowthorne: Transport Research Laboratory.

13. KIMBER, R M (1980). The traffic capacity of roundabouts. Department of

Environment Department of Transport, TRRL Report LR 942: Crowthorne: Transport and Road Research Laboratory.

14. KIMBER, R M and ERICA M HOLLIS (1979). Traffic queues and delays at

road junctions. Department of the Environment Department of Transport, TRRL Report LR 909. Crowthorne: Transport and Road Research Laboratory.

15. KIMBER R M, DALY P, BARTON J, and GIOKAS C (1986). Predicting time-

dependent distributions of queues and delays for road traffic at roundabouts and priority junctions. Journal of the Operational Research Society, 37 (1), pp 87-97 1986

16. KIMBER, R M and HOLLIS, Erica M (1979). Traffic queues and delays at road

junctions. Department of the Environment Department of Transport, TRRL Report LR 909: Crowthorne: Transport and Road Research Laboratory.

17. McDONALD M, N B HOUNSELL and R M KIMBER (1984). Geometric delay

at non-signalised intersections. Department of the Environment Department of Transport, TRRL Report SR 810. Crowthorne: Transport and Road Research Laboratory.

18 MARLOW, M and G MAYCOCK (1982). The effect of Zebra crossings on

junction entry capacities. Department of the Environment Department of Transport, TRRL Report SR 724. Crowthorne: Transport and Road Research Laboratory.

Acknowledgements and references Page 183

19. MAYCOCK, G and HALL, R D (1984) Accidents at 4-arm roundabouts.

Department of the Environment Department of Transport, TRRL Report LR 1120: Crowthorne: Transport and Road Research Laboratory.

20. PICKERING D, R D HALL and M GRIMMER (1986). Accidents at rural T-

junctions. Department of Transport, TRRL Report RR 65. Crowthorne: Transport and Road Research Laboratory.

21 SEMMENS, Marie C (1982). The capacity of some grade-separated roundabout

entries. Department of the Environment Department of Transport, TRRL Report SR 721: Crowthorne: Transport and Road Research Laboratory.

22 SEMMENS, Marie C (1988) The capacity of entries to very large roundabouts.

Department of Transport, TRRL Report RR 142. Crowthorne: Transport and Road Research Laboratory

23. WEBB, PJ and J R PEIRCE (1991). ARCADY/3 User Guide, Department of

Transport, TRL Application Guide AG18. Crowthorne: Transport Research Laboratory.

For further details of these and all other TRL publications, telephone Publication Sales on 01344 770783, or visit TRL on the Internet at www.trl.co.uk

Chapters 10 and 11

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Appendices Page 185

APPENDICES Appendix A - Card image format of data Appendix B - Measurement of the geometric parameters affecting capacity Appendix C - Measurement of the geometric delay parameters Appendix D - Site-specific measurements for capacity corrections Appendix E - Measurement of “Queue Marker” position Appendix F - Measurement of pedestrian crossing geometry Appendix G - Measurement of accident prediction geometry Appendix H - Estimation of circulating flow (CIRFLO) Appendix J - Glossary INDEX

Appendices

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Card Image format of data Page 187

Appendix A - Card image format of data

Please note that this appendix describes the format of the data as saved to the input data file and not as entered via the GUI. The general format of the card images is as follows: *CTxx* ---- CARD TITLE ---- *Heading or data notation data * Card Type 1 - Title and Run Information Card

Rows and Columns Contents Range Row 1, Columns 1-80 Title of run 0 to 80 alphanumeric characters Row 2, Columns 1-80 Location 0 to 80 alphanumeric characters Row 3, Columns 1-80 Date Day Month Year Row 4, Columns 1-80 Client 0 to 80 alphanumeric characters Row 5, Columns 1-80 Enumerator 0 to 80 alphanumeric characters Row 6, Columns 1-80 Job Number 0 to 80 alphanumeric characters Row 7, Columns 1-80 Status 0 to 80 alphanumeric characters (using either

pre-defined or user defined phrases) Rows 8-, Columns 1-80 Description 0 to 80 alphanumeric characters per line. Any

number of lines. Last Row End Marker for Card 1 “End”

The run title is merely for the user's convenience to assist in identifying the input file and output. This card must be the first card of the input file.

e.g. Visual ARCADY 6.00 *CT1* ---- RUN TITLE ---- {run title} {location} {date} {client} {enumerator} {job number} {status} {description is added here and it can can wrap onto multiple lines} End *

Appendix A

Card Type 2 – Modelling time periods Keyword Description

Range

NARMS The number of arms at the roundabout 3-7 START The start time of the modelled period using 24-hour clock

notation (hhmm) 0-2400

FINISH The finish time of the modelled period 0-2400 INTERV The length of each period (minutes) 1-30 VEHLEN The mean vehicle length of a car (1 PCU) including the

separation distance between vehicles. 1-10

The total modelled period must be a whole number of time segments. For example, to model the period 8 am to 9 am in 10-minute intervals at a four-arm roundabout the following parameter card would be appropriate:

&PARAM NARMS=4, START = 0800, FINISH = 0900, INTERV = 10 &END

Card Type 3 - Principal Options The keywords used on the principal options card can be assigned logical data values, and are initially set to false (or switched off) by default. An option keyword can be set to true by an assignment of the form KEYWORD=T. The options permitted within ARCADY are listed below, followed by notes about valid combinations of selected options. Keywords associated with only mini-roundabouts or standard roundabouts are indicated with (Mini) or (Standard). MINI Set to true when modelling a mini-roundabout. LONDON (Mini) Set to true if the mini-roundabout is located in Greater London. DIRECT Set to true when traffic demand data is input directly for each arm for each time segment. LEVELS Set to true when traffic demand is synthesised from flow levels (before the peak, at the

peak, and after the peak) and time data (time at start of peak, when peak is reached and at end of peak period).

FOUR Set to true when traffic demand is synthesised from traffic counts over four consecutive

one-hour periods. (When this demand type option is selected the total length of the modelled period must be four hours).

ODTAB Set to true when traffic demand is synthesised from a peak-hour turning traffic count (of

one-hour duration). (The modelled period must be 90 minutes, allowing 15 minutes before the peak period and 15 minutes after.) If ODTAB is set to true then TPDEF, TPBAL and TPTIME must all be false.


SATN Set to true when only the capacities of the junction are to be calculated under saturated

conditions. Queue-lengths and delays are not modelled. One and only one of the keywords defining demand type (DIRECT, LEVELS, FOUR, ODTAB and SATN) must be set to true. HVDEF Set to true when default percentages of heavy vehicles are to be used. If HVDEF is set to

true then HVTIME and HVTURN must both be false. HVTIME Set to true when the percentage of heavy vehicles is input separately for each time segment. HVTURN Set to true when the percentages of heavy vehicles are input for each turning movement

(rather than for each entry arm). TPDEF Set to true when default values are to be used for turning proportions. If TPDEF is set to

true TPTIME, TPENT and TPBAL must be false. TPTIME Set to true when turning proportions are input (or estimated if TPBAL is true) for each time

segment. TPENT Set to true when turning proportions are input (or estimated if TPBAL is true) for each arm. TPBAL Set to true when turning proportions are estimated from data defining the traffic flow

entering and leaving the junction on each arm. If TPBAL is set to true then TPDEF must be false and TPENT set to true.

GSAME Set to true when a roundabout is symmetrical and the various geometric data items input

are the same for all arms. QBARS Set to true when site-specific observations of mean circulating flows and mean entry flows

are present in the data file (which can be used to make corrections to the capacity formulae).

INTCOR Set to true when corrections to the capacity formulae (intercept corrections) are present in

the data file. These are usually values calculated from observed mean flow values (see QBARS)

USECOR Set to true when correction terms (site-specific intercept corrections) are to be applied to

the capacity formulae. Set to false when site-specific observations are to be used to generate new correction factors AND then apply them.

GEODEL (Standard) Set to true when geometric delays are to be calculated as well as queuing delays. LGSEP (Standard) Set to true when a very large (often grade-separated) roundabout is being

modelled, where the revised capacity relationship in RR142 is applicable to all arms. LDARK (Standard) Set to true when night-time conditions are assumed. This has the effect of

reducing all capacities by five percent. (Daylight is assumed if not set.)

Appendix A

LDAY (Mini) Set to true when day-light conditions only are assumed. This has the effect of

increasing all capacities. (‘Normal’ conditions assumed if neither LDAY or LNIGHT is set) LNIGHT (Mini) Set to true when night-time conditions only are assumed. This has the effect of

reducing all capacities. (‘Normal’ conditions assumed if neither LDAY or LNIGHT is set) The keywords defining lighting conditions (LDAY and LNIGHT) cannot both be set to true. LWET (Mini) Set to true when wet road surface conditions only are assumed. LDRY (Mini) Set to true when dry road surface conditions only are assumed. The keywords defining road surface conditions (LWET and LDRY) cannot both be set to true. MPASS2 Set to true when queue variation calculations are to be made, to provide results for queue

length probability distributions. This can only be done when a data file has first been generated from a previous run, in which MPASS2 has been set to false (this process is carried out automatically by ARCADY).

LMARG Set to true when marginal analysis reports are required. ACCIDS (Standard) Set to true when accident analysis is required. M0 (Mini) Set to true when simple (M0) accident analysis is required. M2 (Mini) Set to true when full (M2) accident analysis is required. QUEVAR Set to true when the day-to-day variability of queue-lengths are to be calculated. CIRFLO (Standard) Set to true when initial estimates of circulating flows (CIRFLO) past each arm

are to be calculated. JOURNEY Set to true when point-to-point journey times are to be calculated. GEODEL must also be

set to True. DEMSET= Indicates the number of sets, e.g. DEMANDSETS=2. Multiple demand sets also affect

cards 15-25. (Range = integer values from 1 to 9) The keywords GEODEL, LGSEP, LDARK, ACCIDS, and CIRFLO do not a apply to mini-roundabouts and are ignored if found when MINI is set to true. Example: For a simple run of the program using default values of turning proportions and heavy

vehicle percentages, and with traffic demand input directly for a standard roundabout the following option card would be appropriate.

&OPTION DIRECT=T, TPDEF=T, HVDEF=T &END


Card Type 4 - ARM NAMES One card is required for each arm of the junction. The cards must be in order of arms (i.e. arm A before arm B etc). Columns Contents Range 1-80 Name of arm 0 to 80 alphanumeric characters The names are used as an aid to identification of arms on the printed output. Card Type 5 (Standard roundabout) - GEOMETRIC DATA One card is required for each arm of the junction, unless GSAME=T in which case only one card is required. The cards must be in order of arms (i.e. arm A before arm B etc). The numeric data is all floating-point type and keywords are alphanumeric. Columns Contents Range 1-10 Approach road half-width, v (metres) for arm I 2 to 12.0 11-20 Entry width, e (metres) for arm i 3.0 to 16.0 (and e > v) 21-30 Average effective length over which flare is

developed, l'(metres) for arm i. If v=e, l' should be set to zero

> 0.0

31-40 Entry radius, r (metres) for arm i > 3.0 41-50 Inscribed circle diameter, D (metres) for arm i > 13.0 51-60 Entry angle, phi (degrees) for arm i 0.0 to 80.0 61-80 Keywords from the following list may be

inserted into these columns as appropriate. They may be in any order and may be separated by blanks or commas.

Keyword LGSEP/ indicates that all arms should have the modified capacity formula applied to them, as LMWAY shown in RR142 EXIT indicates that arm i is one-way only, with no traffic entering the roundabout CONST indicates a zebra crossing on arm i, with a constant pedestrian flow throughout the

modelled period

Appendix A

DIRECT indicates a zebra crossing on arm i, with the pedestrian flows input directly for each time

segment PROFIL indicates a zebra crossing on arm i, with the pedestrian flow following a profile similar in

shape to the vehicular demand on arm i, with the pedestrian demand specified as an average flow per hour over the period

MARK indicates that the user is specifying a queue marker on arm i, for use in reporting on queue

variations. The queue marker details are read from Card Types 13-14.

The prime determinants of entry capacity are e and v, so these should be measured particularly accurately (from the road or large scale plans) whenever possible. When an arm is "exit-only" columns 1-60 should be left blank unless there is a pedestrian crossing on the arm, in which case columns 1-10 should contain the full width of the road.

For any arm the options CONST, DIRECT or PROFIL are mutually exclusive.

In SATN (fully saturated) mode, CONST is the only permitted pedestrian flow type.

Card Type 5 (Mini-roundabout) - GEOMETRIC DATA One card is required for each arm of the junction, unless GSAME=T in which case only one card is required. The cards must be in order of arms (i.e. arm A before arm B etc). The numeric data is all floating-point type and keywords are alphanumeric. Note that the field widths are 8, not 10 as used elsewhere. Columns Contents Range 1-8 Approach road half-width, VF (metres) for arm

i 2.0 to 10.0

9-16 Entry width, e (metres) for arm i 3.0 to 10.0 17-24 Average effective length over which flare is

developed, lm'(metres) for arm i. (Not measured the same way as for a standard roundabout). Set to zero if there is no flare.

0.0 to 45.0

25-32 Minimum approach half-width, Vm (metres) for

arm i 2.0 to 10.0

33-40 Distance between arm i and next arm (metres) 5.0 to 20.0 41-48 Entry corner kerb line (metres) for arm i 2.0 to 40.0 49-56 Gradient on approach over 50 metres

(percentage) -7.0 to 7.0


57-90 Keywords from the following list may be

inserted into these columns as appropriate. They may be in any order and may be separated by blanks or commas.

Keyword KCI indicates the presence of a kerbed central (refuge) island within 20 metres of the junction. PELICAN indicates the presence of a signalised ‘pelican’ crossing on arm. ZEBRA indicates the presence of an unsignalised ‘zebra’ crossing on arm. (none) No crossing on arm. Only one of the keywords PELICAN and ZEBRA can be set to true. CONST indicates crossing has a constant pedestrian flow throughout the modelled period. DIRECT indicates crossing flows are input directly for each time segment. PROFIL indicates crossing flows follow a profile similar in shape to the vehicular demand on arm i,

with the pedestrian demand specified as an average flow per hour over the period. MARK indicates that the user is specifying a queue marker on arm i, for use in reporting on queue

variations. The queue marker details are read from Card Types 13-14.

The prime determinants of entry capacity are e, VF, so these should be measured particularly accurately (from the road or large scale plans) whenever possible.

Exit-only arms on mini-roundabouts cannot be modelled.

In SATN (fully saturated) mode, CONST is the only permitted pedestrian flow type.

Only one of the keywords CONST, DIRECT and PROFIL can be set to true.

Example: * CT5 VF E LM VM A K G 000.00 000.00 000.00 000.00 000.00 000.00 000.00 KCI,PELICAN,DIRECT,MARK 000.00 000.00 000.00 000.00 000.00 000.00 000.00 ZEBRA, CONST 000.00 000.00 000.00 000.00 000.00 000.00 000.00

Appendix A

GEOMETRIC DELAY DATA - Card Types 6 and 7 Cards of type 6 and 7 are required whenever the option GEODEL is true. The measurement of variables for these cards is described in Appendix C. All data is of the floating-point type. Card Type 6 One card is required for each arm of the junction. Note that field widths are 8, not 10 as used elsewhere. Columns Contents Range 1-8 "Approach" speed for light vehicles on arm i,

VA (kph) > 0.0 (or blank - see note below)

9-16 "Departure" speed for light vehicles on arm i,

VD (kph) > 0.0

17-24 Entry angle, ENA (degrees) > 0.0 25-32 Exit angle, EXA (degrees) > 0.0 33-40 Exit radius, EXR (metres) 0.0 to 100.0 41-48 Visibility distance to the right, SD (metres)

for conventional roundabouts. Blank if distance not known, or in the case of non-conventional roundabouts

0.0 to 100.0

49-56 Distance between junction entry and the

centre of the junction, D1 (metres) > 0.0

57-64 Distance between centre of the junction and

the junction exit, D2 (metres) > 0.0

65-72 Angle between arm I and the next arm to the

left (arm i+1 or 1 if i=NARMS), ANGL (degrees) Note: sum of angles must equal 360

any value (including negative)

73-80 Distance travelled along arm (upstream and

downstream) from one measuring point to another (included in point-to-point journey times)

10 to 500

When an arm is exit-only, data should be coded for VD, EXA, EXR, D2 and ANGL.

All other fields should be left blank.


Card Type 7 One card is required for each arm. The cards must be in order of arms (i.e. arm A before arm B etc). Columns Contents Range 1-8 The distance travelled through the junction

from arm i to arm 1, DBC (metres) >0.0 (or blanks - see note below)

9-16 The distance travelled through the junction

from arm i to arm 2, DBC (metres)

-8n The distance travelled through the junction

from arm i to arm n, DBC (metres) (where n is number of arms)

Any Card Type 7 relating to an exit-only arm should have all fields left blank.

SITE-SPECIFIC CORRECTION DATA - Card Types 8-10 Card Types 8 and 9 are required whenever the option QBARS (site-specific observations) is true, and Card Type 10 is required if INTCOR (intercept correction) is true. When INTCOR is true, Card Types 8 and 9 are also retained if they already exist (i.e. if site-specific observations have been previously recorded). Card Type 8 Columns Contents Range 1-10 Observed entry capacity for arm 1 (or blank if

no data available) (PCUs per minute) >0.0 or blanks

11-20 Observed entry capacity for arm 2 (or blank)

(PCUs per minute)

-10n Observed entry capacity for arm n (or blank)

(PCUs per minute) (where n is number of arms)

Card Type 9 Columns Contents Range 1-10 Observed circulating flow at arm 1 (arm A)

corresponding to the entry flows on Card Type 8 (or blank if no data available) (PCUs per minute)

>0.0 or blanks

11-20 Observed circulating flow at arm 2 (arm B)

(or blank) (PCUs per minute)

Appendix A

-10n Observed circulating flow at arm n (or blank)

(PCUs per minute) (where n is number of arms)

Card Type 10 Columns Contents Range 1-10 Intercept correction for arm A calculated in a

previous run of ARCADY (or blank if no correction required) (PCUs per minute)

Any number, including negative or blanks

11-20 Intercept correction (if any) for arm B (PCUs

per minute)

-10n Intercept correction (if any) for arm n (PCUs

per minute) (where n is number of arms)

LARGE ROUNDABOUT DATA - Card Types 11 - 12 These card types are required if LGSEP is set to true. Card Type 11 Columns Contents Range 1-10 Mean circulating flow past arm 1 (PCUs per

minute) > 0

11-20 Mean circulating flow past arm > 0 -10n Mean circulating flow past arm > 0 Card Type 12 Columns Contents Range 1-10 Separation between exit from, and entry to,

the roundabout for arm 1 (metres) > 0

11-20 Separation for arm 2 > 0 -10n Separation for arm n > 0


QUEUE MARKER DATA - Card Types 13 - 14 These cards are required if MARK is set to true on Card Type 5. Card Type 13 Columns Contents Range 1-10 QMARK for arm 1 > 0 11-20 QMARK for arm 2 > 0 -10n QMARK for arm n > 0 Card Type 14 Columns Contents Range 1-10 QFLARE for arm 1 > 0 11-20 QFLARE for arm 2 > 0 -10n QFLARE for arm n > 0 Card Type 15 - DIRECT DEMAND DATA When the DIRECT option is selected, one Card Type 15 is required for each time segment. The card format is used for traffic demand data and, when TPBAL is true, for exit count data. A group of cards for exit data must follow the group for demand data. All data is of the floating-point type. Columns Contents Range 1-10 Demand flow (or exit count) on arm 1 for

time segment j (vehicles per minute) > 0.0

11-20 Demand flow (or exit count) on arm 2 for

time segment j (vehicles per minute) > 0.0

-10n Demand flow (or exit count) on arm n for

time segment j (vehicles per minute) (where n is number of arms)

> 0.0

The field containing traffic demand data for an exit-only arm is left blank.

Appendix A

LEVELS DEMAND DATA - Card Types 16-19 When the LEVELS option is selected one Card Type 16 and one Card Type 18 is required. Card Types 17 and 19 may also be required. These card formats are used for traffic demand data and, when TPBAL is true, for exit count data. A group of cards for exit data must follow the group for demand data. All numeric data is of the integer type for Card Types 16 and 17, and floating-point type for Card Types 18 and 19. One keyword may be used on card types 16 and 18. Any fields relating to traffic demand data on exit-only arms must be left blank. Card Type 16 Columns Contents Range 1-10 Time t1, when demand flow begins to rise

towards peak for first arm (hours, minutes; hhmm)

> Start time

11-20 Time t2, when demand flow reaches peak for

first arm (hhmm) t2 > t1

21-30 Time, t3, when demand flow stops falling

after peak for first arm (hhmm) t3 > t2 Finish time > t3

31-40 May contain the keyword SAME if the data

on the card apply to all arms. If the times are different for the various arms then these columns must be left blank, and a Card Type 17 is required for each remaining arm

Card Type 17 Columns Contents Range 1-10 Time, t1 when demand flow begins to rise

towards peak for arm i (hhmm) > Start time

11-20 Time, t2, when demand flow reaches peak for

arm i (hhmm) t2 > t1

21-30 Time, t3, when demand flow stops falling

after peak for arm i (hhmm) t3 > t2 Finish time > t3


Card Type 18 Columns Contents Range 1-10 Demand flow level before peak, q1, (or exit

count) for first arm (vehicles per minute) > 0.0

11-20 Demand flow level at peak, q2, (or exit count)

for first arm (vehicles per minute) q2 > q1

21-30 Demand flow level after peak, q3, (or exit

count) for first arm (vehicles per minute) q2 > q3 > 0.0

31-40 May contain the keyword SAME if the traffic

demand data apply to all arms. When demands are different for each arm these columns must be left blank and a Card Type 19 is required for each remaining arm.

Card Type 19 Columns Contents Range 1-10 Demand flow level before peak, q1, (or exit

count) for arm i (vehicles per minute) > 0.0

11-20 Demand flow level at peak, q2, (or exit count)

for arm i (vehicles per minute) q2 > q1

21-30 Demand flow level after peak, q3, (or exit

count) for arm i (vehicles per minute) q2 > q3 > 0.0

Example: of Card Type 16, assuming that the parameter START has been set equal to 0745 and

FINISH to 0915: 0800 0820 0845 SAME The corresponding Card Types 18 and 19 might be, assuming different flows on each arm of a three-arm junction: 12.0 18.3 10.9 5.4 8.2 4.25 6.38 7.25 7.0 FOUR HOUR DEMAND DATA - Card Type 20 When the option FOUR is true one Card Type 20 is required for each arm. The cards must be in order of arms (i.e. arm A before arm B etc). This card type is used for traffic demand data and, when TPBAL is true, for exit count data. A group of cards for exit data must follow the group for demand data. All data on the card are of the floating-point type.

Appendix A

Columns Contents Range 1-10 Traffic demand (or exit count) for first one-

hour period for arm i (vehicles) > 0.0

11-20 Traffic demand (or exit count) for second one-


21-30 Traffic demand (or exit count) for third one-


31-40 Traffic demand (or exit count) for fourth one-


The greatest demand for any arm must be in the second or third period.

For an exit-only arm a Card Type 20 with blanks in all fields must be used for traffic demand data. Example: of Card Type 20 for a four-arm roundabout, with arm B exit-only: 630 710 780 700 350 420 400 340 280 320 360 300

ODTAB (O-D TABLE) DEMAND DATA - Card Type 21 When the option ODTAB is true a Card Type 21 is required for each arm. All data on the card are of the floating-point type. Columns Contents Range 1-10 Total traffic demand (vehicles) for one-hour

period from arm i to arm 1 > 0.0

11-20 Total traffic demand (vehicles) for one-hour

period from i to arm 2 > 0.0

-10n Total traffic demand (vehicles) for one-hour

period from arm i to arm n (where n is number of arms)

> 0.0

U-turns can be included in the count as traffic from arm i to arm i.

For an exit-only arm a Card Type 21 with blanks in all fields must be included in the data file.


Example: for a three-arm junction:

0 750 200 300 0 470 250 370 0

PERCENTAGE OF HEAVY VEHICLES - Card Types 22 and 23 Card Types 22 or 23 are required whenever HVDEF is false; Card Type 22 is appropriate if HVTURN is true, otherwise Card Type 23 is used. All data is of the floating-point type. Any fields relating to traffic from exit-only arms may be left blank. Card Type 22 One card is required for each arm of the junction. The cards must be in order of arms (i.e. arm A before arm B etc). If HVTIME is true then the group of cards is repeated for each segment. Columns Contents Range 1-10 Percentage of heavy vehicles in the flow from

arm i to arm 1 0.0 to 100.0

11-20 Percentage of heavy vehicles in the flow from

arm i to arm 2 0.0 to 100.0

-10n Percentage of heavy vehicles in the flow arm i

to arm n (where n is number of arms) 0.0 to 100.0

Card Type 23 One card is required if HVTIME is false, otherwise one for each time segment. Columns Contents Range 1-10 Percentage of heavy vehicles entering the

junction on arm 1 0.0 to 100.0

11-20 Percentage of heavy vehicles entering the

junction on arm 2 0.0 to 100.0

-10n Percentage of heavy vehicles entering the

junction on arm n (where n is number of arms)

0.0 to 100.0

TURNING PROPORTIONS - Card Types 24 and 25 Card Types 24 or 25 are required unless one of TPDEF, TPBAL, or ODTAB is true. Card Type 24 is appropriate if TPENT (but not TPBAL) is true, otherwise Card Type 25. Card Type 24

Appendix A

One card is required for each arm of the junction. The cards must be in order of arms (i.e. arm A before arm B etc). If TPTIME is true then the group of cards is repeated for each time segment. Columns Contents Range 1-10 The proportion (or count in vehicles) of traffic

from arm i to arm 1 > 0.0

11-20 The proportion (or count in vehicles of traffic

form arm i to arm 2 > 0.0

-10n The proportion (or count in vehicles) of traffic

from arm i to arm n (where n is the number of arms)

> 0.0

If the data entered is traffic data, or the sum of the turning proportions on a Card Type 24 is

very close to but not identically 1.0, then the input data is multiplied by a scaling factor so that they form proportions that exactly total to 1.0.

The proportion of traffic from arm i to arm i corresponds to U-turning traffic. For an exit-only arm all fields must be left blank on a Card Type 24.

Card Type 25 One card is required if TPTIME is false, otherwise one for each time segment. The data on Card Type 25 apply to all entry arms of the junction. Columns Contents Range 1-10 Proportion (or count in vehicles) of traffic

taking 1st exit after entry > 0.0

11-20 Proportion (or count in vehicles) of traffic

taking 2nd exit after entry > 0.0

-10n Proportion (or count in vehicles) of traffic

taking nth exit after entry (where n is number of arms)

> 0.0

If the data entered is traffic data, or the sum of the turning proportions on a Card Type 25 is

very close to but not identically 1.0, then the input data is multiplied by a scaling factor so that they form proportions that exactly total to 1.0.

Traffic taking the nth exit is traffic making a U-turn.


Card Types 15-25 (multiple-demand sets) – All Demand Data Formats:

The form of the data depends upon the level of detail provided, e.g. flows entered by demand type, by vehicle type, by arm, etc. This determines the card types required. If only one demand set is defined the complete format of CT15-25 is identical to the ARCADY 5 format. However, if more than one demand set is defined an additional line of data is written to file which stores which of the defined demand sets have been chosen to be run. The format is: Columns Contents Range 5 Demand set 1 selected to run Boolean (0=false, 1-true) 6 Demand set 2 selected to run “ 7 Demand set 3 selected to run “ Etc.. “ 4+n Demand set n selected to run “ This is followed by the required card types, ordered by card type, and within that, by set. The demand data cards 15-21 start with an additional line which stores the Set Title (excluding ‘*’ comment lines). An example is shown below (ODTAB demand data, which has two demand sets defined; the first one selected for analysis; and heavy vehicle percentages defined for each time segment): e.g. * *CT15-25 --- SELECTED DEMAND SETS ---- 10 * *CT21* ---- DEMAND SET TITLE 1 ---- Cross roads, 2 stage, fixed green * *CT21* ---- ORIGIN DESTINATION TABLE 1 ---- FOR PEAK HOUR 0244.0 0000.0 0000.0 0000.0 0000.0 0000.0 0000.0 0085.0 0244.0 * *CT21* ---- DEMAND SET TITLE 2 ---- Additional Development Demand * *CT21* ---- ORIGIN DESTINATION TABLE 2 ---- FOR PEAK HOUR 0244.0 0000.0 0000.0 0000.0 0000.0 0000.0 0000.0 0085.0 0244.0 *NO CT22* * *CT23* ---- PERCENTAGES OF HEAVY VEHICLES 1 ---- FOR EACH SEGMENT * FROM A FROM B FROM C FROM D 010.00 011.00 012.00 013.00 014.00 015.00 016.00 017.00 018.00 019.00 020.00 021.00 022.00 023.00 024.00 025.00 026.00 027.00 028.00 029.00 030.00 031.00 032.00 033.00 *CT23* ---- PERCENTAGES OF HEAVY VEHICLES 2 ---- FOR EACH SEGMENT * FROM A FROM B FROM C FROM D 010.00 011.00 012.00 013.00 014.00 015.00 016.00 017.00 018.00 019.00 020.00 021.00 022.00 023.00 024.00 025.00 026.00 027.00 028.00 029.00 030.00 031.00 032.00 033.00 *NO CT24*

Appendix A

PEDESTRIAN CROSSING DATA - Card Types 26 and 27 Card Type 26 (Zebra crossing) – PEDESTRIAN CROSSING DATA One Card Type 26 is required for each arm which has a pedestrian crossing (indicated by the use of keywords on Card Type 5). The cards should be in order of arms (i.e. arm A before arm B etc). All data is of the floating-point type, except for the arm identifier. The measurement of these parameters is described in Appendix F. There are two formats of this card – format ‘a ‘ for zebra crossings and format ‘b’ for pelican crossings, reflecting the different data required by the two different models. Card Type 26a (Zebra crossing): One Card Type 26 is required for each arm which has a pedestrian crossing (indicated by the use of keywords on Card Type 5). The cards should be in order of arms (i.e. arm A before arm B etc). All data is of the floating-point type, except for the arm identifier. The measurement of these parameters is described in Appendix F. Columns Contents Range 1 Arm Identifier (alphanumeric) A,B...G 2-10 Average pedestrian flow per hour (average

over the period modelled), or blank if crossing has direct demand data

> 0.0

11-20 Reservoir space between crossing and

junction entry, VGAP (vehicles) > 0.0 or blank

21-30 Number of vehicles queueing on exit which

would extend half way across the previous entry, VBLOCK (vehicles)

> 0.0

31-40 Length of pedestrian crossing, XLONG (or

portion across junction entry if crossing has a central refuge) (metres)

> 0.0

41-50 Length of portion of pedestrian crossing

which crosses the junction blank exit, XLONG2 (or blank if crossing has no central refuge) (metres)

> 0.0 or blank

If the arm is exit-only, VGAP and XLONG must be blank. Card Type 26b (Pelican crossing) – PEDESTRIAN CROSSING DATA One Card Type 26 is required for each arm which has a pedestrian crossing (indicated by the use of keywords on Card Type 5). The cards should be in order of arms (i.e. arm A before arm B etc). All data is of the floating-point type, except for the arm identifier. The measurement of these parameters is described in Appendix F. Columns Contents Range


1 Arm Identifier (alphanumeric) A,B...G 2-10 Average pedestrian flow per hour (average

over the period modelled), or blank if crossing has direct demand data

> 0.0

11-20 The amber time preceding a red period

(seconds). > 1.0 [default = 3.0]

21-30 The amount of amber time which can be

regarded as green (seconds). > 0.0 [default = 2.9]

31-40 The time between the traffic signal turning red

and the “green man “ signal appearing (seconds).

> 1.0 [default = 1.0]

41-50 The time period during which the green man

signal is shown D (seconds). > 4.0 [default = 4.0]

51-60 The time period during which the flashing

amber traffic signal is shown (seconds). > 6.0 [ default = 6.0]

61-70 The minimum period for which the traffic

signal remains green after a red period (seconds).

> 6.0 [default = 20.0]

71-80 Reservoir space between crossing and

junction entry, VGAP (PCUs) > 0.0 or blank

If the arm is exit-only, VGAP must be blank. Card Type 27 (Zebra crossing) – PEDESTRIAN ‘DIRECT’ FLOW DATA If any crossing has pedestrian flows input directly (indicated by use of the DIRECT keyword on Card Type 5) then one Card Type 27 is required for each time segment. Data items are only required in fields corresponding to arms with crossings that have pedestrian data input directly, and all data is of the floating-point type. Columns Contents Range 1-10 Pedestrian flow (per minute) for crossing on

arm 1 in time segment or j, if crossing has direct demand data, otherwise blanks

> 0.0 or blanks

11-20 Pedestrian flow (per minute) for crossing on

arm 2 in time segment or j, if crossing has direct demand data, otherwise blanks

> 0.0 or blanks

Appendix A

-10n Pedestrian flow (per minute) for crossing on

arm n in time segment or j, if crossing has direct demand data, otherwise blanks (where n is number of arms)

> 0.0 or blanks

Card Type 27 (Pelican crossing) – PEDESTRIAN ‘DIRECT’ FLOW DATA The same data is required as for the zebra crossing data, and hence the same card type format is used. N.B. In ARCADY 6 the existing ARCADY 5 Zebra crossing model is used for BOTH standard roundabout AND mini-roundabouts. The separate mini-roundabout model (in ARCADY 5) is no longer used for Pelican OR Zebra crossings.


ACCIDENT PREDICTION DATA - Card Types 28-30 For mini-roundabouts Card Types 28 and 30 must be entered for any form of accident analysis. If only simple (flow-based) analysis is required, Card Types 29a, 29b, 29c, and 29d may be omitted – these cards are required for full accident analysis, involving junction geometry, etc. Only simple accident analysis is available for standard-roundabouts and this requires card types 28, 29 and 30. The measurement of the geometric parameters for Card Types 28 and 29 are described in Appendix G. The format of the accident Card Types 28, 29 and 30 are different depending on whether

the roundabout is a standard or mini-roundabout. Card Types 29a, 29b and 29c also differ depending on whether the junction is a 3-arm or 4-arm mini-roundabout. For a 3-arm mini-roundabout Card Type 29c is not required.

Card Type 28 Columns Contents Range 1-10 Central island diameter, CID (metres).

(Blank if a mini-roundabout is being modelled)

> 4.0

11-30 Keywords from the following table may be

inserted into these columns as appropriate. They may be in any order, may be separated by blanks or commas and are alphanumeric

Appendix A

Keyword The following keywords are used to describe the traffic flow data period: 12HR indicates that traffic flow data on CT30 are for a 12 hour period. AADT indicates that traffic flow data on CT30 are Average Annual Daily Totals. (none) indicates that traffic flow data on CT30 are for a 16 hour period. One of the following four keywords must be used to describe the traffic flow data: ENT is used when the only traffic inputs are junction entry flows for each arm (not permitted if there are any entry-only arms) ENEX is used when junction entry and exit flows are input for each arm, but circulating flows are

not available CIRC is used when entry, exit and circulating flows are input for all arms PART is used when entry, exit and circulating flows are input for some, but not all, arms One of the following three keywords must be used to describe the site type (as defined in the COBA9 manual): URB Main-Urban INT Inter-Urban REC Recreational/Inter-Urban One of the following six keywords must be used to indicate in which month the traffic data were collected:

APR April AUG August MAY May SEP September JUN June OCT October

Card Type 29 (Standard roundabout) One card is required for each arm of the junction. If the arm is exit-only (or accident predictions are not required for this arm) then the card must be left blank. All numeric data is of the floating-point type (and may take negative values) and the keywords are alphanumeric. Columns Contents Range 1-10 Entry path curvature (metres-1), CE for arm i -0.01 to +0.05 11-20 Approach curvature (metres-1), CA for arm i -0.025 to +0.033 21-30 The angle between the approach arm and the

next arm (clockwise) around the junction 40.0 to 150.0

31-40 This field contains the keyword YBAR when

yellow bars are present on arm i, otherwise blanks

Card Type 30 (Standard roundabout)


One card is required for each arm of the junction. The keywords used on Card Type 28 indicate which traffic data items are entered, and columns must be left blank where no data is entered. All traffic counts are for a 16-hour period unless one of the two keywords (12HR, AADT) are specified on Card Type 28. When the PART keyword is used a blank card must be input for an arm where accident predictions are not required. All data is of the floating-point type. Columns Contents Range 1-10 Total traffic entering from arm i (in thousands

of vehicles) including motorcycles > 0.0

11-20 Total motorcycles entering from arm i (in

thousands) > 0.0

21-30 Total traffic exiting on arm i (in thousands of

vehicles including motorcycles) > 0.0 or blanks

31-40 Total motorcycles exiting on arm I (in

thousands) > 0.0 or blanks

41-50 Total traffic circulating past arm i (in

thousands of vehicles including motorcycles) > 0.0 or blanks

51-60 Total motorcycles circulating past arm i (in

thousands) > 0.0 or blanks

61-70 Pedestrian flow across arm i (in thousands),

input when pedestrian accidents are to be calculated

> 0.0 or blanks

Exit flows are not required if entry and circulating flows are provided and pedestrian

accidents are not to be calculated. Card Type 29a (3-arm Mini-roundabout) One card is required for each arm of a 3-arm mini-roundabout. Columns Contents Range 1-8 Entry corner kerb line distance for arm i

(metres) 2.0 to 40.0

9-16 Minimum exit width for arm i (metres) 1.8 to 7.0 17-24 Width of entry along give-way of arm i


25-32 Angle between arm i and arm (i+1) (degrees) 0.0 to 200.0

Appendix A

33-40 Gradient on arm i approach over 50 metres

(degrees) -15.0 to +15.0

41-48 Sight distance to right from 4m on arm i

(metres) 0.0 to 300.0

49-56 Sight distance to right from 50m on arm i

(metres) 0.0 to 300.0

Card Type 29b (3-arm Mini-roundabout) One card is required for each arm of a 3-arm mini-roundabout. Columns Contents Range 1-8 Number of side roads within 20 metres on exit

side of arm i 0 or 1

9-16 Number of entry lanes on approach of arm i 1 or 2 17-24 Number of exit lanes on arm i 1 or 2 25-32 Major junction within 200 metres on a arm i 0 or 1 33-40 Shops within 20 metres on arm i or arm (i+1)

exit 0 or 1

41-48 Single or double yellow or zigzag markings

within 20 metres on exit side of arm i 0 or 1

49-56 Length of any island, including hatching, on

arm i 0.0 to 100.0

Card Type 29a (4-arm Mini-roundabout) One card is required for each arm of a 4-arm mini-roundabout. Columns Contents Range 1-8 Entry corner kerb line distance for arm i


9-16 Junction centre to kerb distance for arm i


17-24 Effective flare length* for arm i (metres). Set

to 0 metres if there is no flare. 0.0 to 45.0

25-32 Minimum exit width within 50 metres on arm

i (metres) 1.8 to 7.0


33-40 Minimum distance from junction centre to

projected arm centre line for arm i (metres) -4.0 to +10.0

41-48 Angle between arm i and arm (i+1) at 20

metres (degrees) 0.0 to 180.0

49-56 Angle between arm i and arm (i+1) at 0

metres (degrees) 0.0 to 180.0

57-64 Distance from junction centre to offside end

of give-way line of arm i (metres) 3.0 to 17.0

Card Type 29b (4-arm Mini-roundabout) One card is required for each arm of a 4-arm mini-roundabout. Columns Contents Range 1-8 Approach curvature within 100 metres on

arm i Left/Straight/right and Slight/moderate/sharp

9-16 Presence of curvature on entry path on arm i 1=Absent; 2=Present 17-24 Major junction within 200 metres on arm i 0 or 1 25-32 Guard rail on exit side of arm i 0 or 1 33-40 Sight distance ahead from 0 metres on arm i

(metres) 0 to 300.0

41-48 Sight distance to right from 4 metres on arm i

(metres) -20 to +300.0

49-56 Sight distance to right from 50 metres on

arm i (metres) -20 to +300.0

Card Type 29c (4-arm Mini-roundabout) One card is required for each arm of a 4-arm mini-roundabout. Columns Contents Range 1-8 Roundabout has a domed central island 0 or 1 9-16 Shopping land use within 20 metres of

roundabout 0 or 1

Card Type 30 (Simple Accident, M0) (Mini-roundabout) One card is required for each arm of a 3 or 4-arm mini-roundabout.

Appendix A

Columns Contents Range 1-10 Total traffic (in 1000s of vehicles) entering

from arm i and leaving at Arm A 0 to 20

11-20 Total traffic (in 1000s of vehicles) entering

from arm i and leaving at Arm B 0 to 20


from arm i and leaving at Arm C 0 to 20


from arm i and leaving at Arm D 0 to 20

41-50 Two-way pedestrian flow (in 1000s) across

arm i 0 to 20

Card Type 30 (Simple Accident, M0) (Mini-roundabout) Cards are required for each arm of a 3 or 4-arm mini-roundabout, in order, representing traffic turning from arm i to arms A, B C and D respectively (3 cards for 3-arm roundabouts and 4 cards for 4-arm roundabouts). Columns Contents Range 1-10 Total light vehicles (in 1000s) entering from

arm i and leaving at arm A 0 to 20

11-20 Total medium vehicles (in 1000s) entering

from arm i and leaving at arm A 0 to 20

21-30 Total heavy vehicles (in 1000s) entering from


31-40 Total buses (in 1000s) entering from arm i

and leaving at arm A 0 to 20

41-50 Total motorcycles (in 1000s) entering from


51-60 Total bicycles (in 1000s) entering from arm i

and leaving at arm A 0 to 20

QUEUE VARIATION DATA - Card Type 31 Calculations using queue variations involve running the program twice (described as a two-pass process). The queue variation parameters are written to a temporary file, which is separate from the data file, after a first pass of the program. The values are automatically appended to the data file in order to conduct a second pass, which will produce the queue variability results. The temporary file is then deleted.


Card Type 31 Columns Contents Range 1-10 Start of peak in demand Not applicable 11-20 End of peak in demand (Enter the values output from

the first run) 21-30 Time of maximum demand 31-40 Average traffic capacity 41-50 Average traffic intensity 51-60 Run down time Card Type 32 – Arm Angles and scaling factors One Card Type 32 is required for each arm. The angle between each arm of the junction is used only by the Junction Diagram, i.e. this information is not used by the ARCADY model. The card also contains flow scaling factors that are applied to the traffic demand data prior to any calculations. A value of 100% represents “no scaling”, while a value of 0% represents “no traffic”. The cards should be in order of arms (i.e. arm A before arm B etc). All data is integer, except for the arm identifier. Columns Contents Range 1 Arm Identifier (alphanumeric) A,B...G 2-10 The angle between the arm and its immediate

next arm 0-360

11-20 The flow scaling factor (%) applied to the

traffic data (for both demand and accident data AND for all demand sets) for each arm

0-999

Appendix A

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Measurement of geometric parameters affecting capacity Page 215

Appendix B - Measurement of the geometric parameters affecting capacity The geometric parameters used in the calculation of capacity are split between those which apply to ALL roundabouts, standard roundabouts and mini-roundabouts. They are as follows:

B.1 All roundabouts

i) The approach road half-width, v, is measured at a point in the approach upstream from any entry flare, from the median line to the nearside kerb, along a normal (see figure B-1).

Figure B-1 Geometric parameters (i)

ii) The entry width, e, is measured from the point A along the normal to the nearside kerb (see figure B-1). AB = e (the point A is as in figure B-1).

Appendix B

iii) Effective flare length: The construction to be used to obtain the average effective

length over which the flare is developed, l´, is illustrated in figure B-2.

Where: AB = e (the point A is as in figure B-1).

GH = v (the point G is the best estimate of the start of the flare).

GD is parallel to AH and distance v from it.

CF´ is parallel to BG and distance ½ BD from it.

The simplest way to do this is as follows:

1. If not already done so, draw the projection line AB as used to measure the entry width (see above).

2. Draw ‘tram lines’ parallel to the centre of the road, towards the give-way line,

from the point G at the start of the flare.

Tip: The point G can often be chosen by identifying the first point upstream of the giveway line where the nearside kerb and centre line of the road are parallel to each other. Also note that on occasions when the line A-B is NOT perpendicular to the island kerb (or centre line) the line D-A is not always (v) wide

3. This line (GD) intersects the line AB, which is the line along which the entry

width (e) is measured, at point D. The flare length (l’) is measured from the point C, which bisects BD along a line parallel to the kerb and distance ½ BD from it, to a point F´ where it intersects line GD.

The effective flare length is then defined as l´ = CF´. (The line over which l´ is measured is often curved as it matches the curve of the nearside kerb.)

The effective flare length is recorded as zero if there is no flare.


Figure B-2 Geometric parameters (ii)

Tip: Measurement of median line In order to measure some parameters, it is first necessary to define a line “midway” between the kerbline and centre line (or centre island) on the entry to the roundabout. It is sometimes also necessary to define a midway line on the roundabout exits.

Naturally, the midway line (or centre line, or median line) passes through all the centre points. Each centre point is defined as the centre of a line drawn from kerb to centre line (or island) at right angles to the kerbline

Appendix B

B.2 Standard roundabouts

iv) The conflict (entry) angle, φ, serves as a geometric proxy for the conflict angle between entering and circulating streams. Two constructions are used for φ : the first applies to well-defined conventional roundabouts, and the second to all other types.

For conventional roundabouts (i.e. those with identifiably parallel-sided weaving

sections) the construction is illustrated in Figure B-3 where:

A´D´ is a line parallel to the path taken by the circulating flow, along the centre of the circulating carriageway. EF is a line midway (along its entire length) between the nearside kerbline and the median line or nearside edge of any median island. BC is a tangent to EF at the point where EF intersects the give-way line. φ is then measured as the angle between BC and the tangent to A´D´ at the point of intersection of the two lines.

Figure B-3 Geometric parameters (iii)


For all other cases the construction is as in Figure B-4 where:

EF and BC are as in Figure B-3 JK is as EF but for the following exit. GH is a tangent to JK at the point where JK intersects the boundary of the roundabout circulation. L is the point of intersection between BC and GH.

φ is then defined as 2GLB) (angle

-90 except that if a zero or negative

value results from this construction (i.e. angle GLB > 180) then φ shall be taken to be zero.

Figure B-4 Geometric parameters (iv)

Appendix B

v) The entry radius, r, is measured as the minimum radius of curvature of the

nearside kerbline at entry, see Figure B-1. For some designs the arc of minimum radius may extend into the following exit, but this is not important provided that a half or more of the arc length is within the entry region.

When the radius of the kerbline is continuously changing (i.e. it is a transitional curve) TRL recommend measuring the entry radius as follows: 1. De-lineate a length of kerbline which extends from a point 25 metres

upstream of the give-way line to 10 metres downstream of the give-way line (measured along the curved path of the nearside kerbline).

2. Within the length of kerbline defined above, choose a 20 metre length with

the maximum average curvature (i.e. this 20 metre length has a greater average curvature than any other 20 metre length you could have chosen). This process will have to be done by eye and is therefore somewhat subjective. (If the length of kerbline in (1.) is less than 20 metres long, then use whatever length is available for defining (2.)).

3. Measure the average radius of the 20-metre length defined in (2.). This measurement becomes “r”.

vi) The inscribed circle diameter, D, is the diameter of the largest circle that can be

inscribed within the junction outline (see figure B-1). In cases where the outline is asymmetric, the local value in the region of the entry considered is taken.

vii) The entry to exit separation, SEP, is the distance (metres) between the centres of

the entry and previous exit (on the same arm) measured around the roundabout perimeter (see figure B-5).


Figure B-5 Geometric parameters (v)

The lettering convention of Figures B-1 to B-4 follows that of LR 942 (Kimber 1980) to which the user can refer for further information.

B.3 Mini-roundabouts

viii) The minimum approach road half-width, Vm, is the minimum approach half-width, measured anywhere within the final 100 metres of the approach.

ix) The effective flare length*, l´m, is the average effective flare length, constructed

in the same way as for iii) but using Vm, the minimum approach road half-width, as the approach width instead of the approach road half-width. (see figure B-2)

x) The distance to next arm, An, is the straight line distance from the offside end of

the give-way line on the current arm to the nearest point of the median marker or island (whichever is nearest) on the next arm after that (see Figure B-6). It represents “weaving length” as described in LR942 (Kimber, 1980).

It is the value of A(n+1) corresponding to the next arm clockwise which affects the capacity on arm n rather than the value of An.

Appendix B

The program requires the values to be entered as described in order to simplify the data-entry process.

Figure B-6 Geometric parameters (vi)

xi) The entry corner kerb line distance, K, is the length of the entry corner kerb line, measured from a point on the entry kerb from which a perpendicular would be raised to the offside end of the give-way line, to a point further along the kerb from which a perpendicular would be raised to the offside end of the exit width measurement on the next arm clockwise (see figure B-6)

xii) The gradient over 50m, G50, is the gradient measured on the approach over the

last 50 metres prior to the entry.

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Measurement of geometric delay parameters Page 223

Appendix C - Measurement of the geometric delay parameters i) The construction required in the measurement of the entry angle, ENA, is shown

in Figure C-1. The line EF is a straight line along the centre of the arm from a point upstream of

any local flaring or curvature which may be present to deflect entry traffic. GH is parallel to the nearside kerbline at the approach to the junction and at a

distance of 2 metres from it. JK is a curve drawn at a distance of 2 metres from the central island in the area of

the junction entry. When possible, PQ is drawn as a common tangent to the curves GH and JK. The entry angle, ENA, is measured as that between the lines EF and PQ. When

no common tangent can be drawn to the two curves the entry angle takes the value 0.

Figure C-1 Geometric delay parameters - angles

Appendix C

ii) The exit angle, EXA, is measured in a similar manner to ENA (see figure C-1),

but using curves VW and KL in the junction exit area. A common tangent is drawn (whenever possible) and the exit angle, EXA, is the angle between this tangent and the line EF.

iii) The exit radius, EXR, is the minimum radius of the nearside kerbline at the exit

from the roundabout to the arm in question. (This is similar to the entry radius described in Appendix B, page 215.

iv) The sight distance, SD, is the visibility to the right to the most distant circulating

vehicle that an approaching driver can see, measured from a point 15 metres upstream of the entry and at a height of 1.05 metres. The measurement is along a curve following the outer kerbline of the circulating area. The line ST on Figure C-2 gives an example of the measurement in the particular example. If not known, this value should not be guessed at; specify zero instead. ARCADY will then use a revised model which does not require it.

v) The measurement of the distance, D1, from junction entry to centre of the

junction is shown in Figure C-2. The point X is the midpoint of the central island, whether or not the island is circular. The distance D1 is measured from the point X to the junction entry at a point midway between the nearside kerbline and the median line of the arm.

vi) The distance D2 is measured from the centre of the junction (point X in Figure C-

2) to the junction exit. vii) To measure the angles between arms the required construction is illustrated in

Figure C-1. The angle to be measured, ANGL, is that between the line EF for the arm in question and that associated with the following arm, that is the line XY. If the alignment of two adjacent arms is such that they are parallel or even diverge as they approach the junction, then the measured angles should be treated as 0 and negative respectively. The sum of the angles measured between each pair of arms must be 360 degrees.

viii) The distances through the junction from one arm to another, are measured along a

typical path taken by a vehicle making the turning movement from the junction entry to the junction exit.

Measurement of geometric delay parameters Page 225

Figure C-2 Geometric delay parameters - distances

Appendix C

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Site-specific measurements for capacity corrections Page 227

Appendix D - Site-specific measurements for capacity correction To correct the capacity formula for local conditions the following procedure should be adopted. The relevant entry must be substantially overloaded during peak periods before these measurements can be made. On-site counts are made of the total inflow (light and heavy vehicles) from the entry and the corresponding circulating flow across the entry (light and heavy vehicles) for successive minutes during which there is continuous queuing in all available lanes in the approach to the entry. (There need not necessarily be queues in all lanes at the give-way line). Queuing on the approach should occur continuously for periods of twenty minutes or more during peak periods. The approach queues should be stable for at least five vehicle lengths upstream of any entry widening. At minimum, a total of sixty minutes of saturation should be obtained. (Note that, when counting circulating flow for any arm, traffic exiting by that arm should not be included, but traffic exiting by the next or successive arms should be (see figure 3-1)). The mean entry flow QEBAR and mean circulating flow QCBAR are calculated for all of the saturated minutes together, both in pcu/minute, assuming 2 PCUs for each heavy vehicle. When site-specific data is being collected for arms with pedestrian crossings care should be taken in making observations. It is essential that the junction entry is operating under saturated conditions, and is not affected by the crossing. This requires traffic queuing at the junction entry at all times, downstream of the crossing. Observations should not be made when there is any blocking back into the junction, whether it be due to a pedestrian crossing on the next arm, or for any other reason.

Appendix D

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Measurement of the “Queue Marker” position Page 229

Appendix E - Measurement of “Queue Marker” position The distance from the critical queue point to the give way line must be expressed as two values, QMARK and QFLARE, as shown in Figure E-1.

(i) QMARK is the distance, in metres from the queue marker to the start of the flare (from which point the number of vehicles queuing side-by-side will become indeterminate). N.B. The queue marker must be upstream of the flared section. If there is no flare, QMARK is simply the distance from the queue marker to the give-way line.

(ii) QFLARE is the average number of “passenger car units” (pcu) normally queuing

in the flared area up to the give-way line. If there is no flared area, then QFLARE is set to zero. A pcu is equivalent to 1 light vehicle or ½ a heavy vehicle.

Figure E-1 Measurements required to define a critical queue point

Appendix E

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Measurement of pedestrian crossing geometry Page 231

Appendix F - Measurement of pedestrian crossing geometry i) VGAP is the average number of vehicles which can be held in the reservoir space

(in all lanes) between the pedestrian crossing and the junction entry, the shaded area X in Figure F-1. A suitable value for the average length of space occupied by a queuing vehicle would be 5.75 metres/pcu.

ii) VBLOCK is the average number of vehicles in a queue at the pedestrian crossing on

an exit from the junction which would reach back into the junction and block half of the previous junction entry. This is the number of vehicles which would fill the shaded area Y in Figure F-1.

iii) The length of the pedestrian crossing, XLONG, is measured from kerb to kerb

unless there is a central refuge. In this case two distances are measured, XLONG corresponding to the part of the crossing across the junction entry and XLONG2 for the junction exit portion.

Figure F-1 Measurement of reservoir spaces for crossing on arm B

Appendix F

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Measurement of accident prediction geometry Page 233

Appendix G - Measurement of accident prediction geometry The traffic flow circulating past an arm consists of traffic making several turning movements and is shown as QC in Figure 3-1. It does not include any traffic to or from the arm under consideration. The geometric parameters used in the calculation of accident frequencies/indices are split between those which apply to ALL roundabouts, standard roundabouts and mini-roundabouts. They are as follows: G.1 All roundabouts

i) The effective flare length, (measured in metres) is measured in the same manner as illustrated in Appendix B.1(iii), “Measurement of the geometric parameters affecting capacity”. Recorded as zero if there is no flare.

ii) Pedestrian flows: (Two-way flows measured in 1000’s). All pedestrians crossing

the road within 20 metres of the give-way line are included. Flows on a pedestrian crossing should be included if the edge of the crossing nearest the give-way line is within 20 metres. Any pedestrians crossing the centre of the roundabout should be included in the corresponding movement(s) across the nearest arm(s).

G.2 Standard roundabouts

iii) The entry path curvature (i.e. the reciprocal of the minimum value of Re in metres - see Figure G-1) is defined in terms of the shortest path for a vehicle taking the second exit* from the roundabout. Consider a vehicle making a through movement to the second exit at the roundabout in the absence of other traffic. Starting approximately 50m back from the give-way line, construct a path 2m wide with flowing curves representing the shortest path the vehicle could take through the roundabout keeping on its own side of the road but otherwise ignoring lane markings. The heavy line in Figure G-1 represents the locus of one such path. Note: normally the path is assumed to start 1 metre from the nearside kerbline (as in Figure G-1), but it may also start 1 metre from the carriageway dividing line or kerbline of a central reserve, or anywhere between these two points. The entry path curvature for a given path is the maximum curvature in the region of the entry. The final resultant entry path curvature for the entry (CE) is the minimum entry path curvature obtainable from all possible paths. The sign convention is that the curvature is positive if deflection is to the left, and negative if it is to the right. Straight paths are recorded as giving a curvature of zero.

* The only exception is at a roundabout which has been installed at a T-junction, where a vehicular path entering the roundabout on the head of the “T” should also leave on the head of the “T”.

Appendix G

iv) Angle between arms: The angle (θ) between the approach arm and the next arm clockwise (in degrees) is the angle subtended by projections of the relevant approach centre lines as shown in Figure G-1. If the approaches are curved then the tangents to the centre line at the entry points (P) are used for this construction.

Figure G-1 Accident data parameters (standard roundabouts)

Approach radius (+Ra)

Approach radius (-Ra)

50 - 500 metres

Ca = 1/ Ra

Ignore this bend

Figure G-2 Approach curvature (standard roundabouts)


v) The central island diameter, CID, (measured in metres) is in cases of non-circular

islands the maximum value . vi) The approach curvature, Ca, (measured in metres) is defined in terms of that

section of the junction approach road within the range from about 50m (to be clear of the immediate entry geometry) to 500m from the roundabout give-way line. Ca is the maximum curvature (the reciprocal of the minimum radius in metres) of the bend nearest to the junction within this section of the approach. Figure G-2 illustrates this parameter in two cases. The sign convention is that right-hand bends (approaching the roundabout) are positive and left-hand bends are negative. A straight approach has C = 0.

G.3 Mini-roundabouts

vii) The minimum exit width (measured in metres) is the minimum exit width (e.g. opposite a refuge) within 50 metres, or clear of the preceding junction (whichever is the closest).

Arm A

Arm B

Arm C

C

A3

A1

A2

C3

Arm D

K2

Figure G-3 Accident data parameters (mini-roundabouts)

viii) The entry width along give-way (measured in metres): If there is a splitter island,

the complete length along both parts of the give-way line and across the front of that island should be recorded.

Appendix G

ix) The minimum distance from junction centre to projected arm centre line (measured

in metres): This is the length of a normal from the projected centre line tangent at An to C, i.e. from Cn to C (see Figure G-3). The value is negative if the projected centre line is to the right of C, otherwise it is positive.

x) The minimum distance from junction centre to entry corner kerb line (measured in

metres) is the distance from the centre C of the central island to the point Kn on the entry kerb of arm n which is nearest to the central island. (see Figure G-3.)

xi) The distance from junction centre to offside end of give-way line (measured in

metres) is the distance from the centre of the island C to the to the point An. (see Figure G-3.)

xii) The length of island (measured in metres) is the overall length (including hatching)

of an island, any part of which is within 20 metres of the give-way line. The island may be kerbed only, hatched only, or both, and may or may not continue beyond 20 metres. Islands at pedestrian crossings are included. Where pedestrian gaps exist the island should be treated as continuous.

Figure G-4 Angle between arms [n] and [n+1] at 0m and 20m (mini-roundabouts)


xiii) The angle between arms [n] and [n+1] at 20m (measured in degrees) should be measured between the tangents to the centre lines or entry side of an island at 20 metres. (See Figure G-4.)

xiv) The angle between arms [n] and [n+1] at 0m (measured in degrees) should be

measured between the tangents to the centre lines or entry side of an island at 0 metres. (See Figure G-4.)

xv) The gradient from 50-100m on approach (measured as a percentage) should be the

average gradient of the approach measured between 50-100 metres from the junction.

xvi) The sight distance right/ahead (measured in metres) should be measured, ideally,

using an observer height of 1.05 metres and a target height of 0.26 metres (car tail lights). The observer should view from the indicated distances back from An along the middle of arm n. The target should be on the nearside. For sight distance to the right, the position of the target should be recorded from the ‘datum’ point D(n-1). N.B. The result should be recorded as negative if the target is forward of the datum point. For sight distance ahead at 4-arm mini roundabouts the distance should be measured in the same way as the distance right, i.e. the position of the target should be recorded from the ‘datum’ point D(n-2). (see Figure G-5.)

Arm A

Arm B

Arm C

A1

A2D1

50m

Sight distancefrom 50m (Arm B)

A4

4m

Arm D

Sight distancefrom 4m (Arm D)

Figure G-5 Sight distance right/ahead (Mini roundabouts)

Appendix G

xvii) The number of entry and exit lanes: The number of entry lanes on the approach

should be recorded upstream of any flaring, or at 100 metres, or clear of the preceding junction (whichever is closest), but not nearer than 20 metres. The number of exit lanes should be recorded at the same point.

xviii) The presence of entry path curvature indicates the presence of entry deflection on

the "practical path" for any turning movement, taking account of lane markings.

In order to measure entry path curvature, it is necessary to construct the centre line of the smoothest possible path through the junction. The vehicle should be assumed to be 2 metres wide so that the centre line of its path is at least 1 metre from the nearside kerb, any kerbed island, or any lane used for travel in the opposite direction. The radius of curvature should be measured in the vicinity of the entry. The vehicle path curvature is the inverse of the radius. Straight paths have a curvature of zero. A ‘practical’ vehicle path is used to determine the presence of any entry path curvature. Unlike the ‘classic’ vehicle path that keeps to the correct side of the island and is no closer than 1 metre to it, the ‘realistic’ path allows the vehicle to pass over, or around the wrong side of the central island if it is a shorter path. For the ‘practical’ path the ‘realistic’ path should be assumed if the central island is flat and the ‘classic’ path otherwise. Lane lines should be taken into account. Assume that the vehicle will use the left lane for a left turn, the right most lane for a right turn and whichever gives the shortest smooth path for a straight ahead movement. The path should keep at least 1 metre away from any hatched area or from the edges of whichever lane it uses at any particular time, unless the lane is less than 2 metres wide, in which case the path should follow the centre of the lane. In any cases where the resulting curvature of the ‘practical’ path is tighter than 5 metres (the minimum turning circle of a typical car) the realistic path should be used. The presence of entry path curvature (taking account of lane markings) can usually be assessed without making the measurements.

xix) The approach curvature within 100 metres is the curvature of the arm on the

approach to the junction upstream of any local flaring. It assessed on a 7-point scale from “sharp” to “moderate” to “slight” in either direction, plus “straight”.

Estimation of circulating flow (CIRFLO) Page 239

Appendix H - Estimation of circulating flow (CIRFLO) One of the variables used in modelling large and/or grade-separated roundabouts is the circulating flow past the arm in question, during the central 30 minutes of the modelled period (section 7.10, page 105). When modelling new junctions it is, of course, not possible to measure any flows directly, and various methods of estimating them are used. Given that demand flows have been estimated rather than measured, the following describes a satisfactory method of estimating circulating flows (CIRFLO) - its accuracy will be in keeping with the accuracy of the demand flows. The method should be used only when circulating flows cannot be measured directly. The automatic initial estimation of CIRFLO can be specified in “Principal Options”. The method, as described below, is used to calculate the circulating flows. When an analysis run is requested the program will ask the user to confirm that new circulating flows are to be estimated from the supplied demand data. The calculated values overwrite the values (if any) previously entered via the geometric data window. For a four-arm roundabout, the maximum circulating flow past each arm, assuming there are no U-turners, is as follows:

CircA = Flow (D → B) + Flow(D → C) + Flow(C → B) .............….……….…(1) CircB = Flow (D → C) + Flow(A → C) + Flow(A → D) ........…………...…… (2) CircC = Flow (A → D) + Flow(B → D) + Flow(B → A) …….............….…… (3) CircD = Flow (B → A) + Flow(C → A) + Flow(C → B) ..................………….(4)

The flows for the O/D movements given above should be known for the central hour of the modelled period, since these will have been used to specify the demand flows on each arm. According to the ARCADY method for synthesising the shape of the peak profile, the demand flows for the peak half hour will be 55 percent of the peak hour flows.

So the maximum circulating flow past Arm A (for example) during the central 30 minutes of the peak hour flow will be: 0.55 (Flow (D→B) + Flow (D→C) + Flow (C→B)) veh (or pcu) .....…....……….. (5) i.e. 1.10 (Flow (D→B) + Flow (D→C) + Flow (C→B)) veh (or pcu) per hour ………. (6)

The maximum circulating flow takes no account of suppressed demand - it assumes that no arms are overloaded. In practice, it is likely that the junction will be overloaded during the central 30 minutes of the modelled period, and this will reduce all circulating flows. If, for example, all circulating flows were reduced by 10 percent (a typical figure) then the best initial estimate of CIRFLO (again using Arm A as an example) would be:

Appendix H

0.90 x 1.10 (Flow (D→B) + Flow (D→C) + Flow (C→B)) veh (or pcu) per hour …(7) Equation (7) is approximately equal to equation (1) so it is sufficiently accurate to use equations 1 to 4 as initial estimates of CIRFLO for each arm. i.e. CIRFLO past Arm A = Flow (D → B) + Flow(D → C) + Flow(C → B) where all the units are in vehicles (or pcu) per hour. The initial estimates of circulating flows (CIRFLO) past each arm can be used during a first pass of the program. This first pass will enable a better estimate of circulating flows to be made, based on the amount of traffic emerging from each arm, and the turning proportions, during the central 30 minutes of the modelled period. The amount of traffic emerging from each arm is equal to the demand flow or capacity of the arm, whichever is the lesser. Both demand flow and capacity can be read from the program output, for each time segment throughout the modelled period. The turning proportions can be assumed to be the same as those entered in the Origin-Destination table in the program input. Better estimates of the circulating flows can then be made, using equations (1) to (4) but with the flows on the right-hand side of the equations now based on traffic emerging from each arm, rather than the demand flow on each arm. These better estimates of CIRFLO can then be used in a second pass of the program. In principle, it would be necessary to repeat this process for a series of iterations, to gradually home-in on the most appropriate correct circulating flows. In practice, it has been found that the circulating flows used in this second pass are sufficiently close to the true values, particularly given the accuracy of the original demand flows from which they are derived. It should be borne in mind that the iterative process referred to above is necessary only when arms are overloaded - in this case the entry flows affect, and are affected by, the circulating flows. If no arms are overloaded during the central 30 minutes of the modelled period, the circulating flows can be obtained directly from the demand flows, with no iterative process being necessary.

ARCADY only provides the initial estimates of CIRFLO. It takes no account of the potential differences between the demand data and the amount of traffic emerging from each arm.

Glossary Page 241

Appendix J – Glossary AADT Flow Average Annual Daily Total traffic flow Approach half-width The same as “approach width” – it is the width of the side of the carriageway which is approaching the junction, measured at a point upstream from any entry flare, from the median line to the nearside kerb, along a normal. Arriving-vehicle delay An estimate of average delay per vehicle on a given arm arriving during a particular time period, which takes account of the changing situation from time segment to time segment. At-grade roundabout Opposite of grade-separated (see grade-separated roundabout) Average delay extra time to negotiate the junction, due to the presence of other traffic, averaged over many occasions (e.g. the delay between 5.15 and 5.25 pm averaged over many days). Average queue-length the number of vehicles on a arm waiting to enter the junction averaged over many occasions. Card type a term continued in ARCADY that dates back to the use of computer punch cards. Junction data values are split into logical groupings (card types) to facilitate the reading and saving of data as well as the program coding of ARCADY. Circulating flow flow on the circulating carriageway crossing an entry. Conventional roundabout A roundabout with identifiably parallel-sided weaving sections. This definition is used to determine the appropriate method of measuring the conflict (entry) angle, φ.

Appendix J

Crosswalk See Zebra crossing. Demand flow the number of vehicles per unit time wishing to use a traffic stream or junction. This is the “Design Reference Flow” used in Departmental Standard TD 42/95, 1995. DMRB Design Manual for Roads and Bridges Entry capacity the maximum inflow from an entry (no. of vehicles per unit time). It is observable only when the demand flow at that entry is sufficient to cause continuous queuing on the approach. Entry flow the number of vehicles per unit time entering a junction from a particular arm. Entry path curvature The inverse of the entry path radius. Entry path radius The inverse of the entry path curvature. The entry path radius is a measure of the deflection to the left imposed on vehicles entering a roundabout. Entry path radius is the commonly referred to term in TD16/07, instead of the entry path curvature which was the more commonly referred to term in the older TD16/93. Full capacity (of a junction) the maximum inflow that a junction can accommodate under fully saturated conditions for the given set of turning movements and traffic composition. Fully saturated junction having demand flow on all arms sufficient to cause continuous queuing. Geometric characteristics/parameters details of the physical layout of the junction.

Glossary Page 243

Geometric delay delay suffered by each vehicle due to the presence of the junction even in the absence of other traffic. Grade-separated roundabout a roundabout with: i) a road (trunk or motorway) passing above or below it. OR ii) a motorway linking directly with it. Headway the time between the fronts of two successive vehicles or pedestrians. Heavy vehicle a vehicle with more than 4 tyres in contact with the road (includes buses, cars pulling trailers and caravans, etc). Intercept maximum entry flow with zero circulating traffic. Light vehicle a vehicle with 3 or 4 tyres in contact with the ground. Mid-block crossing See Pelican crossing Passenger car equivalent (PCE) See ‘PCU’.

Appendix J

Passenger car unit (PCU) A unit of measurement of traffic flow or capacity - equivalent to that of a single car. The PCU equivalent of vehicles of each type (for the purpose of site-specific correction data) are as follows:

Code Vehicle type description PCU factor

1 Cars/light goods (3/4 tyres) 1 2 Medium goods (two axles but >4 tyres 1.5 3 Heavy goods (more than two axles) 2.3 4 Buses/coaches 2.0 5 Motorcycles 0.4 6 Bicycles 0.2

When differentiating between just two classes of vehicles (lights and heavies) the following values are used:

Vehicle type description PCU factor

Light vehicle (3/4 tyres) 1 Heavy vehicle (>4 tyres including buses, cars pulling trailers and caravans, etc.)

2.0

Pelican Crossing signalled pedestrian crossing. Puffin Crossing Signalled pedestrian crossing with pedestrian detection. Queue marker the position along an approach to a junction at which the queue suddenly reaches a critical point (as defined by the user). RFC ratio of demand flow to capacity (see also Traffic intensity).

Glossary Page 245

Roundabouts: normal roundabout - A roundabout having a one-way circulatory carriageway around a kerbed central island 4m or more in diameter and usually with flared approaches to allow multiple vehicle entry.

mini roundabout – A roundabout having a one-way circulatory carriageway around a flush or slightly raised circular marking less than 4m in diameter and with or without flared approaches. (A few roundabouts that have a central island diameter greater than 4m are designed to allow vehicles to run over them and therefore operate in the same way.) Slope rate of change of the entry capacity with the circulating flow. Time-dependent queuing theory the theory used for predicting average queue-lengths (averaged over many occasions) which takes into account the effects caused by the random differences in capacity and arrival rates over the range from individual vehicles to weekly (or even longer) fluctuations. The theory does not account for long term trends, however. Time segment short part of a period modelled in a program interval run, during which demand flows and capacities are considered to be constant. Typically 10 or 15 minutes. Traffic intensity the ratio of demand flow to capacity (RFC). Traffic stream vehicles within or approaching a junction which are considered together for the purpose of determining capacities, queues and delays. At roundabouts the traffic on each approach shares a common entry capacity and in this sense is treated as a single stream. Truck See ‘Heavy Vehicle’ Zebra Crossing Unsignalled pedestrian crossing

Appendix J

INDEX 3-arm roundabout, 15 4-arm roundabout, 19, 34, 165, 174 4-hour traffic counts, 122 About Box, 91 accident analysis, 103 additional design factors, 11 analysis output file, 44, 52, 57 angle between arms, 112, 224 angle between arms, 133 approach curvature, 25, 133, 233, 235, 236,

237, 238 approach half-width, 13, 106, 107, 215 ARCADY 5 files, 56 arm names, 98 ASCII output file, 43 between sites variation, 23 blocking back, 21 capacity correction (site specific), 115 capacity formula corrections, 227 capacity formulae, 23 capacity relationships for mini-roundabouts, 13 central island diameter, 131, 235 checklist, 47 circulating flow, 12, 25, 109, 239, 240 COBA10, 1, 20, 112 COBA9, 20, 131 conflict (entry) angle, 106, 108 consequence warnings, 94 context-sensitive help, 49 crossing capacity, 22 crossing data (output), 153 deceleration rate, 18 default turning proportions, 34, 35, 103 Demand Data (output), 150 demand data graphs (output), 151 demand data type, 99 design tips, 49 DIRECT, 27 direct entry flows, 121 distance from centre to entry/exit, 112 distance from give-way line, 117 distances through junction, 224 domed central island, 141 drive-on-the-right/left, 6 effective flare length, 216, 233 email a report, 74 end time, 96 entry angle, 18, 25, 112, 218, 223, 241

entry capacity, 12 entry corner kerbline distance, 108 entry curvature, 133 entry demand flows, 40 entry flow, 25 entry lanes, 138 entry link speed, 112 entry path curvature, 25, 233 entry radius, 13, 106, 108, 220 entry width, 13, 15, 25, 26, 106, 108, 137, 179,

215, 235 entry-exit separation, 109 error messages, 91, 173, 177, 178 exit angle, 18, 112, 224 exit count data, 40 exit flows, 40 exit lanes, 138 exit link speed, 112 exit only arm, 106, 108 exit radius, 18, 112, 224 Exporting output data, 83 flare length, 13, 25, 106, 107, 216 flare storage, 117 flow data corrections, 102 FOUR, 27 fully saturated conditions, 33 Furness iteration, 34 geometric data (output), 147 geometric delay, 18, 99 geometric delay (output), 156, 163 geometric parameters, 40 grade-separated, 24, 35, 40, 101 Graph Designer, 75 graphical interface, 47 Graphs, 77 hard disk space, 7 hardware requirements, 7 heavy vehicle proportions, 125 Heavy vehicle proportions (output), 150 heavy vehicles, 35, 100 help file, 6 help tips, 90 HTML report, 44 HTML View, 72 inclusive queuing delay, 41 initial circulating flows, 101 input data file, 43 inscribed circle diameter, 13, 18, 25, 106, 220

Index Page 247

Interaction between arms, 14 interval, 97 island diameter, 25 junction diagram, 57 junction image file, 44 junction type, 98 labelling procedure, 16 LEVELS, 27 main menu, 47 marginal analysis, 25, 103 marginal analysis (output), 157 mean circulationg flow, 114 mean entry flow, 114 mean queues, 17 minimum approach half-width, 221 missing or incomplete data, 52 modelling period, 96 Multiple Demand Sets, 118 multiple stream queueing, 17 night time conditions, 101 numerical accuracy, 42 ODTAB, 27 on-site observations, 23 Output and its Interpretation, 143 pedestrian accidents, 19 pedestrian crossings, 126, 129, 134, 231 pedestrian flow profile, 21 pedestrian flows, 25, 40 personal injury accidents, 19 point-to-point journey times, 36 printing ASCII text, 82 Printing from the VIEWER, 82 puffin crossings, 110 queue and delays (output), 154 queue diangrams (output), 158 queue marker, 17, 229 queue marker, 116 queue variability (output), 162 queue variation, 45, 99, 103 queuing theories, 15 Report Designer, 61 report output file (HTM file), 44

report output file (VAR file), 43 report template file, 44 Report Viewer, 71 RFC, 41 RFC graph (output), 160 RFC threshold level, 87 rising, peak and falling flows, 121 road lighting, 35 run title, 95 segment length, 97 separatation of entry and exit slip roads, 24 side roads, 138 sight distance, 112, 140, 224 single-island roundabouts, 1 site ‘type’, 20 site-specific correction, 23 site-specific data, 102 software bulletin, i software requirements, 7 Standard View, 71 start time, 96 starting ARCADY, 95 Steady-state theory, 15 support (product advice), i suppressed demand, 239 synthesised profile, 27 time-dependent queuing theory, 11, 15 total queuing delay, 41 traffic collection month, 131 traffic flows (accident data), 130, 132, 134, 135 Traffic Software News Periodical, i training courses, 11 turning counts, 123, 125 turning proportions, 34, 40, 103, 124 two-pass process, 44 types of turn, 18 US customary units, 87 U-turning traffic, 35 visibility, 18, 112, 224 warning messages, 41 yellow bars, 133 zebra crossings, 21, 110

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