THE MIDLANDS DRIVER INFORMATION SYSTEM: OPERATIONAL EXPERIENCE AND FINDINGS

PJ C Carden, I Beck, R J Meekums

SUMMARY .

Stage 1 of the Midlands Driver Information System has been operational since October 1996, it was officially switched on by the Minister for Roads and Railways, Mr John Watts. With five months of experience of operating the system this paper is able to report both the status of the project overall and the ways in which the largest driver information system in England is being used by the 14 police forces within its boundaries.

Within the project driver information is provided by variable message signs located at key route choice junctions in the network. Two signs are located prior to each junction. The road network which is covered by this system is limited to the motorways within the boundary and those hunk roads which are likely to be able to cany diverted traffic for most of the day. The Stage 1 central control system comprises two hub and spoke systems to set the variable message signs from Perry Barr, north of Birmingham, and Welwyn, Hertfordshire, Police Control Offices. The instation control equipment is a derivative of the stand alone controller developed for the Highways Agency and recently used on the Kent Comdor project.

Over the past five months there has been growing use of the system. From the outset police control offices used to managing variable message signs started using the system regularly. Since then their use has spread and plans are now being set to assist with local traffic conditions as well as strategic diversions from all of the police control offices. To illustrate the diversion affects which can occur through setting strategic plans, traffk flows during an incident on the M42 have been analysed. The effect of the diversion is discussed in the final section of the paper.

PROJECT HISTORY

The initial concept for the project was developed in the early 1990s. A feasibility study, commissioned by the Highways Agency Midlands Network Management Division concluded in 1993 that a driver information system based on up to three control centres and using variable message signs to disseminate information to drivers would be economically justifiable. The anticipated capital costs were f 16 million and with operating costs in the order of €1.3 million per year a benefidcost ratio of at least 2.8: 1 was predicted.

Consultancy commissions were awarded in autumn 1994 to implement the project in two modules, see Figure 1. The project objective was to design the driver information system in such a way as to only offer altemative routes via motorways or high quality dual carriageway all-purpose trunk roads. In addition to this information had to be both directly relevant to the motorists who received it and sufficiently remote from the atypical network delays to allow effective diversion routes.

Mott MacDonald, working in association with MVA Systematica, was awarded the commission for the Midlands Module. As with the Eastem Module of the project this required the design of the infrastructure required for variable message signs but it also included responsibility for procurement of the network management system for the Midlands Driver Information System as a whole. Variable message signs were installed in both modules within the first 24 months of the project and, as has been noted above, Stage 1 of the Midlands Driver Information System became operational in October 1996. This system allows signs to be set throughout each module from their

P J C Carden & R J Meekums - Mott MacDonald Ian Beck - Highways Agency Midlands Network Management Division

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respective control centres at Perry Barr and Welwyn and this represents a significant advance on a European scale in the ability to manage a motorway network over such large areas.

Stage 2 of the project, the Network Management System, is now being developed by BAeSEMA. This will provide an improved interface to the network operator, it will allow real time traffic flow information to be processed to monitor conditions on alternative route options and facilitate automatic performance monitoring to take place. Stage 2 is scheduled to be operational in Spring 1998.

INFRASTRUCTURE FOR A DRIVER INFORMATION SYSTEM

As has been noted above, within this project information is provided to motorists via variable message signs. These were selected in preference to radio based methods in that the information may be read by all motorists passing a sign and they are a well proven, low risk, technology.

After much consultation with the Highways Agency on the merit of providing more or less information it was agreed that the signs should have the capacity to display messages with three lines each of eighteen characters in length. The messages detail the problem on a route, the destination to which the message refers and, where appropriate, the recommended diversion route. With this size of sign it is not necessary to abbreviate destination names within the messages displayed. The message structure complies with the principles of the VAMOS White Book and the Traffk Signs Regulations and General Directions 1994. It should be noted however, that the V M O S suggestion that the predicted duration of the incident is also provided has not been adopted. The reasons for this are two fold, firstly the message length would significantly exceed the seven word maximum recommended by VAMOS and secondly due to concerns over legal liabilities associated with providing inaccuracy delay related information. The estimated duration of an incident is however utilised by the system as part of the diversion plan setting strategy.

The variable message signs are located in pairs, before the 1 mile and !4 mile (or the ?h mile and ’h mile) on the approach to junctions in accordance with the Department of Transport advice. The junctions at which variable message signs are installed were identified within the feasibility study, they are shown in Figure 1.

The driver information system has been designed to restrict diversion routes to those parts of the trunk road network which are likely to be able to accommodate for most of the day additional traffic during atypical conditions. As a result of this the network is restricted to all motorways and only a few trunk roads.

Project has resulted in 70 new Variable message signs being installed and makes use of two existing fixed text, rotating plank, type signs. These in addition to the ten existing 3*16 character signs on the approaches to Birmingham will enable the Midlands Driver Information System to display messages on some 80 variable message signs, hence the claim that this is one of the largest systems of its type in Europe.

The diversion plans set in the event of an incident have been defined from an intuitive look at the road network and extensive discussion with the fourteen police forces managing the strategic road network affected by the Project. This element of the project has proceeded smoothly due to the significant support provided by the police forces involved. Having agreed all of the plans with them, there should always be a recognisable link between incidents on the road network and the information displayed to motorists.

Communications between the signs and police control offices and between the police control offices and network management centres are carried on the existing Highways Agency communications network. In this way the project has developed in a cost effective manner and has made best use of the existing infrastructure. The communications structure is shown in Figure 2, and it may be seen that the architecture has a hub-and-spoke structure. During Stage 1 this limits Network Management Centres to control variable message signs in ‘their’ module, in Stage 2 of the project, the link between Network Management Centres will be activated and this will allow network wide plans to be implemented form either of the centres.

The Stage 1 Network Management Centres and Police Control Office terminals have been provided by adaptaitons of the stand alone controller developed by Simulations Systems Limited for the Kent Corridor Project. The system

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allows police forces to report incidents through the computer terminals giving information on the location, seventy and anticipated duration of the incident. The network management centre stand alone controller analyses the information and identifies possible plans which might be introduced to assist with diverting traffic away from the atypical delays. Its operator, typically the control room traffic supervisor, selects the most appropriate plan to be actioned. The system broadcasts this information to the affected police control offices who are reminded to provide any update information on network constraints within their area. Following a ten minute period, which allows for these responses, the system will set the plan unless additional and constraining information has been supplied by the police forces. During the incident the system consults the police force which is managing the incident to gather update information on how it is propssing and when both the road and queue will be cleared. When the road is clear, the system will clear down all signs set.

The system also allows the signs to be used to assist with local incidents, for instance, queues related to minor incidents, high winds or pedestrians on the carriageway. These are set by each force on the signs within their area. In the event of a variable message sign with a local message being displayed being required for a strategic diversion route message, the latter takes priority.

During Stage 2 of the project, the network management centre systems will be replaced with Network Management Systems. As has been noted above these will make use of real-time traffic flow data which will be derived from stand alone MIDAS equipment operating in each police control office. The project records traffic flows at intersections in the network. The data are transmitted to the central system at 15 minute intervals. In addition to this the selection of diversion route options will take place on the application of rules rather than the simple look-up table approach of the Stage 1 implementation. To assist with the management of the network the new computers will provide greatly enhanced monitoring facilities which will enable diversion route selection logic to be improved as experience is gathered on operating the driver information system.

The police control office terminals based on the stand alone controller will continue to operate until COBS becomes available in each police control office. Thereafter interface to the network management system will be through standard COBS operator interface "inals. In due course, when the message signs sub-system is operational with COBS, setting of variable message signs will transfer away from the stand alone controller and be handled, in conjunction with legends on enhanced message signals and motorway signals, by the message signs sub-system.

OPERATIONAL EXPERIENCE

Prior to the integrated system becoming available police officers in Perry Barr had been used to setting local diversion plans on the ten existing variable message signs on the motorway approaches to Birmingham. These signs had a limited message set, 16 messages were allowed for each pair of signs, however, with their usage these officers were familiar with the concept and benefits which could accrue for management of incidents through the use of providing condition information to motorists on variable message signs. This has formed a robust base from which to build the operational experience of the Midlands Driver Information System.

Training has been provided to all police forces by the consultants responsible for each module. In general police operation control rooms, such as the Hertfordshire Police operations centre at Welwyn, large numbers of officers have been trained and refresher sessions have been provided to accommodate the change of staff through the shift patterns. Dedicated motorway control rooms have required less training input.

At the present time strategic plans spanning a number of police control office areas are only being implemented for incidents which result in a carriageway being closed for an hour or more. The reason for this is that, until Stage 2, the network management system will not have knowledge about the traffic conditions on the diversion route. To maintain system credibility a conservative approach has been taken and for lesser incidents information only plans, those which advise of the problem without a diversion route, are being used.

Figure 3 shows the frequency of use of variable message signs in the Perry Barr network management centre during the months since October 1996. Figure 4 shows, as an example, the types of messages displayed in December 1996. From this it is clear that advice on delays ahead is frequently used, strategic diversion messages are as one

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would expect from the current constraints set comparatively rarely. Logs of plan setting instructions show that between 10 and 20 plans are currently being set per month.

THE EFFECTS OF AN INCIDENT

As a result of an accident on the M42 south of the National Exhibition Centre the north bound carriageway of the’ M42 was closed for two hours. The traffic flows on the roads in the area have been considered as an example of the effect of setting one of the strategic plans. Figure 5 shows the location of the incident and Figure 6 shows the change in traffk flows on three of the affected links. These data have been derived from Highways Agency permanent count sites, with Stage 2 of the Midlands Driver Information System it will be possible to undertake an appraisal in much greater detail.

The data relates to an incident on the M42 northbound between Junction 5 and 6 near to the National Exhibition Centre and Birmingham Airport. A plan was set at 11:47hrs and removed at 13:49hrs. The diversion route used the M42 southbound and the M5 northbound and M6. (See Figure 5 inset). Messages relating to the incident were displayed on the M40 northbound and the M5 northbound advising drivers to avoid the M42 northbound and use the M5/M6 instead.

The top graph in Figure 6 indicates that during the incident period there was a significant reduction in flow on the Northbound M42. This will in part represents ‘trapped’ traffic being almost stationary on the links approaching the incident. The reduction in flow is therefore not likely to be totally related to the diversion strategy. The central graph on Figure 6 shows the link downstream of the incident location, here a substantial reduction in flow takes place during the incident. Following the removal of the plan there is also a two hour lag before the flow reaches average daily flows. This may be due to, either, the incident was not cleared as early as had been perceived in the control room; or radio and TV broadcasts may have continued to broadcast diversion advice after the incident had cleared; or the standing queue of traffic on the M42 south of the incident continued to cause an obstruction for some time after the actual incident had cleared. The lower graph on Figure 6 indicates a substantial increase in flow on the diversion route on the M5 northbound which it is considered can only be due to traffic from the M40 and the M5 taking account of the messages and using the diversion route.

CONCLUSIONS

This paper has outlined the operation of the Midlands Driver Information System, its use by operators and the benefits that have been obtained by the use of the system.

It has been demonstrated that the system produces benefits in terms of diverting traffic away from incident locations on to routes where the delay is likely to be considerably less. Further developments of the system will bring additional benefits and will automate much of the system operation. Using the MCONTRM model of the Midlands Driver Information System road network Mott MacDonald is undertaking further work to quantify the financial benefits of using the system to establish diversion route strategies. From these analyses it will be possible to refine the assessments made during the feasibility study stage of the project.

ACKNOWLEDGEMENTS

This paper draws on work undertaken for the Highways Agency’s Midlands Network Management Directorate and is published with the permission of its Director. The views contained in this paper are those of the authors and not of the Department of Transport nor the Highways Agency.

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