REAM Guidelines On Geometric Design of Roads

F'OITEWORD

Road Engineering Association of Malaysia (REAM), througlr the cooperation and support ofvarious road authorities and engineering institutions in Malaysia, publishes a series of officialdocuments on STANDARD SPECIFICATIONS, GUIDELINES, MANUALS andTECHNICAL NOTES which are related to road engineering. The aim of such publications isto achieve quality and consistency in road and highway construction.

The cooperating bodies are:-

Public Works Department, MalaysiaMalaysian Highway AuthorityInstitution of Engineers, MalaysiaInstitution of Highways & Transportation (Malaysian Branch)

The production of such documents are carried out through several stages. The documents areinitially compiled/drafted by the relevant Technical Committee and subsequently scrutinisedby the relevant Standing Committee of REAM. They are finally endorsed by road authoritiesand practitioners of road engineering at a conference/workshop before publication. REAMwelcomes feedback and suggestions which can update and improve these documents.

This GUIDE ON GEOMETRIC DESIGN OF ROADS is the revision of the existingArahan Teknik (Jalan) 8/86 "A Guide on Geometric Design of Roads" published by JabatanKerja Raya.

The revision was undertaken by the Standing Committee on Technology and RoadManagement of the Road Engineering Association of Malaysia (REAM) with the mandategiven by the Director-General of Public Works Department, Malaysia.

The draft of this Arahan Teknik was presented and discussed at the Forum on Technologyand Road Management in November 1997 and the 4th Maiaysian Road Conference inNovember 2000.

It is hoped that this Guide will address the shortcomings of Arahan Teknik (Jalan) 8/86 andwill be accepted by the highway engineering fraternity in the country.

ROAD ENGINEERING ASSOCIATION OF MALAYSIA46-4, Jalan Bola Tarnpar 13114, Section 13,40100 Shah Alam, Selangor, Malaysia.

Tel:603-55136521 Fax:603-55136523 e-mail:[email protected]

ROAD ENGINEERING ASSOCIATION OF MALAYSIA

A GUIDE ON GEOMETRIC DESIGN OF ROADS

TABLE OF CONTENTS

INDEX

I. INTRODUCTION

2. ROAD CLASSIFICATIONS AND DESIGN STANDARDS

PAGE NO.

I

2.1

2.2

2.3

)4

J.l

J.Z

3.3

J-+

3.5

4.1

A'

+.J

4.4

5.1

5.2

5.3

5.4

5.5

5.6

5.7

11

ll12

l.+

18

20

ROAD CLASSIFICATION / HIERARCHY

DESIGN STANDARDS FOR ROADS

ACCESS CONTROL

SELECTION OF DESIGN STANDARDS

z

2

5

6

8

25

25

a1J+

44

52

DESIGN CONTROL AND CRITERIA

TOPOGRAPHY AND LAND USE

TRAFFIC

DESIGN VEHICLES CHARACTERISTICS

SPEED

CAPACITY

A ELEMENTS OF DESIGN

SIGHT DISTANCE

HORIZONTAL ALIGNMENT

VERTICAL ALIGNMENT

COMBINATION OF HORIZONTAL AND VERTICAL

ALIGNMENT

5. CROSS SECTION ELEMENTS

PAVEMENT

LANE WIDTH & MARGINAL STRIPS

SHOULDERS

KERBS

SIDEWALKS

TRAFFIC BARRIERS

MEDIANS

61

6l

62

62

66

69

6q

69

INDEX

6.

5.8

5.9

5. l0

5.t I

TABLE OF CONTENTS (Cont'd)

SERVICE ROADS

U-TURN

BRIDGE AND STRUCTURE CROSS SECTION

BUS LAYBYES

PAGE NO.

10

73

16

to

OTHER ELEMENTS AFFECTING GEOMETRIC DESIGN 80

6.I ROAD SAFETY 80

6.2 DRAINAGE 80

6.3 LIGHTING 8I

6.4 UTILITIES 81

6.5 SIGNING AND MARKINGS 8I

6.6 TRAFFIC SIGNALS 8I

6.1 EROSION CONTROL, LANDSCAPE DEVELOPMENT 82

AND ENVIRONMENTAL IMPACTS

TABLES

TABLE 2-I

TABLE2-2A

TABLE2-28

TABLE 2-3

TABLE 3.1

TABLE 3-2A

TABLE 3-2B

TABLE 3-3

TABLE 3-4

TABLE 3-5A

TABLE 3-58

TABLE 4-1

TABLE4-2

TABLE 4-3

TABLE 4-4

TABLE 4-5

TABLE 4-6

TABLE4.]A

TABLE 4-78

TABLE 4-8

TABLE 4-9A

TABLE 4-98

TABLE 4-9C

TABLE 4-9D

TABLE 4-9E

TABLE 4-9F


CHARACTERISTICS OF ROAD CATEGORIES

SELECTION OF ACCESS CONTROL (RURAL)

SELECTION OF ACCESS CONTROL (URBAN)

SELECTION OF DESIGN STANDARD

DIMENSION OF DESIGN VEHICLES

DESIGN SPEED FOR RURAL ROADS

DESIGN SPEED FOR URBAN ROADS

CONVERSION FACTORS TO P.C.U.

LEVELS OF SERVICE

DESIGN LEVEL OF SERVICE AND VOLUME/

CAPACITY RATIO (RURAL)

DESIGN LEVEL OF SERVICE AND VOLUME/

CAPACITY RATIO (URBAN)

MINIMUM STOPPING DISTANCE

EFFECTS OF GRADES IN STOPPING SIGHT

DISTANCE _ WET CONDITIONS

DECISION SIGHT DISTANCE

MINIMUM PASSING SIGHT DISTANCES

(2LANE-2WAY)

MINIMUM RADIUS

RELATIONSHIP OF DESIGN SPEED TO MAXIMUM

RELATIVE PROFILE GRADIENTS

MAXIMUM GRADES FOR R5 STANDARD ROADS

MAXIMUM GRADES FOR U5 STANDARD ROADS

MAXIMUM GRADES FOR U6 AND R6 STANDARD

ROADS

PAGE NO.

AT

8

8

9

14

19

1q

2l

22

aA

24

zo

2'7

28

30

3s

5l

DESIGN SUPERELEVATION TABLE (RURAL) 38

DESIGN SUPERELEVATION TABLE (URBAN) 39

PAVEMENT WIDENING ON OPEN ROAD CURVES 43

MAXIMUM GRADES FOR RI. R2. Ul & U2 45

STANDARD ROADS

MAXIMUM GRADES FOR R3 AND R4 STANDARD 45

ROADS

MAXIMUM GRADES FOR U3 AND U4 STANDARD 45

ROADS

A<

46

ul

TABLES

TABLE 4-1OA

TABLE 4-IOB

TABLE 5-1

TABLE 5-2

TABLE 5-3A

TABLE 5-3B

TABLE 5-4

TABLE 5-5A

TABLE 5-58

TABLE 5-6


CREST VERTICAL CURVE (K VALUES)

SAG VERTICAL CURVE (K VALUES)

TYPICAL PAVEMENT SURFACE TYPE

LANE & MARGINAL STRIP WIDTHS

USABLE SHOULDER WiDTH (RURAL)

PAVED SHOULDER WIDTH (URBAN)

PAVED SHOULDER WIDTH (RURAL)

MEDIAN WIDTH (RURAL)

MEDIAN WrDTH (URBAN)

DESIRABLE DISTANCE BETWEEN U-TURNS

PAGE NO.

50

51

6l

6l

64

65

65

70

70

74

FIGUR.ES

FIGURE 2-I

FIGURE 3-1

FIGURE 3-2

FIGURE 3-3

FIGURE 3-4

FIGUR.E 4-1

FIGURE 4-2

FIGURE 4-3

FIGURE 4-4

FIGURE 4-5

FIGURE 4-6

FIGURE 4-6

FIGURE 4-6

FIGURE 4-6

FIGURE 4-6

FIGURE 4.6

FIGURE 4-6

FIGURE 5-1

FIGURE 5-2A

FIGURE 5-28

FIGURE 5-3

FIGURE 5-4

FIGURE 5-5

FIGURE 5-6

FIGURE 5-7


PAGES NO

FLOW CHART FOR SELECION OFDESIGN STANDARDS IO

P DESIGN VEHICLE 15

SU DESIGN VEHICLE 16

WB-15 DESIGN VEHICLE I1

RELATIONSHIP OF LEVEL OF SERVICE TO OPERATING 23

SPEED AND VOLUME / CAPACITY RATIO

MEASURING SIGHT DISTANCE ON PLAN

MEASURING SIGHT DISTANCE ON PROFILE

COMPARISON OF SIDE FRICTION FACTORS ASSUMED

FOR DESIGN OF DIFFERENT TYPES OF ROADS

DIAGRAMMATIC PROFILES SHOWING METHODS OF

ATTAINiNG SUPERELEVATION

CRITICAL LENGTHS OF GRADE FOR DESIGN FOR

TYPICAL HEAVY TRUCK OF 180kg/kw.

A&BC&DE&FG,H&IJ,K&LM

N

TYPICAL CROSS SECTION OF SHOULDER AND VERGE

ROAD KERB DETAILS

ROAD KERB DETAILS

TWO-WAY SERVICE ROAD

MINIMUM DESIGN FOR DIRECTU-TURNS

TYPICAL BRIDGE CROSS SECTIONS

CLEARANCES AT UNDERPASS

LAYOUT OF BUS LAYBYES

32

JJ

35

4]

4't

<A

55

56

57

58

59

60

63

67

68

72

'75

77

18

'79

.*1i 'i{F,:i'. Ei:. "'r:' iisif-.:" ;l ::5;;r.?;

A Guide on Geometric Design of Roads

CHAPTER 1 - INTRODUCTION

This Guide is limited to the geometric features of road design as distinguished from structural

design. It is intended as a manual on the geometric design of road, inclusive both

in rural as well as in urban conditions. The geometric design of road is only applicable to

Rural or Urban areas as specifically indicated in this Guide.

This Guide is to be applied to all new construction and improvements of roads for vehicular

traffic. Comments from users will be most welcomed as this Guide will continue to be updated

from time to time.

This Guide is to be used in conjunction with other Arahan Tekniks that have been or

will be produced by Jabatan Keria Raya or other Agencies.

A Guide on Geometrtc Design of Roads

CHAPTER 2 - ROAD CLASSIFICATIONS AND DESIGN STANDARDS

2.r ROAp CLASSTFTCATTON / HrERARelgy

2.1.1 The Importance of Road Classification

The importance of defining a hierarchy of roads is that it can help clarify policiesconcerning the highway aspects of individual planning decisions on properties served bythe road concerned. Further'more specific planning criteria could be developed andapplied according to a road's designation in the hierarchy: for example design speed,width of carriageway, control over pedestrian, intersections, frontage access etc. In thisway the planning objectives would be clear for each level of road in the hierarchy andpolicies on development control and traffic management would reinforce one another.

2.1.2 Functions of Road

Each road has its function according to its role either in the National Network, RegionalNetwork, State Network or City/Town Network. The most basic function of a road istransportation. This can be further divided into two sub-functions; namely mobility andaccessibility. However, these two sub-functions are in trade off. To enhance one, theother must be limited. In rural areas, roads are divided into five categories, narnely,EXPRESSWAY, HIGHWAY, PRIMARY ROAD, SECONDARY ROAD ANdMINOR ROAD. In urban areas, roads are divided into four categories, namelyEXPRESSWAY, ARTERIAL, COLLECTOR and LOCAL STREET. They are inascending order of accessibility and thus in descending order of mobility.

2.1.3 Road Category and Their Application

Categories of Road

2 GROUPS

URBAN (4 Categories)

1. Expressway2. Arterial3. Collector4. Local Street

RURAL (5 Categories)

l. Expressway 4. Secondary Road2. Highway 5. Minor Road3. Primary Road

A Guid.e on Geometric Design af Roads

Categories of roads in Malaysia are defined by their general functions as follows:

(a) Expresswav

An Expressway is a divided highway for through traffic with full control ofaccess and always with grade separations at all intersections'

In rural areas, they apply to the interstate highways for through traffic and form

the basic framework of National road transportation for fast travelling. They

serve long trips and provide'higher speed of travelling and comfort. To maintaiu

this, they are fully access controlled and are designed to the highest standards.In

urban areas, they form the basic framework of road transportation system in

urbanised area for through traffic. They also serve relatively long trips and

smooth traffic flow and with full access control and complements the Rural

Expressway.

HighwayThey constitute the interstate national network for intermediate traffic volumes

and complements the expressway network. They usually link up directly or

indirectly the Federal Capital, State capitals, large urban centres and points ofentry/exit to the country. They serve long to intermediate trip lengths. Speed oftravel is not as important as in an Expressway but relatively high to medium

speed is necessary. Smooth traffic is provided wrth partial access control.

Primary Roads

They constitute the major roads forming the basic network of the road

transportation system within a state. They serve intermediate trip lengths and

medium travelling speeds. Smooth traffic is provided with partial access

control.They usually link the State Capitals and district Capitals or other Major

Towns.

Secondary Roads

They constitute the major roads forming the basic network of the road

transportation system within a District or Regional Development Areas. They

serve intermediate trip lengths with partial access control. They usually link up

the major towns within the District or Regional Development Area.

Minor Roads

They apply to all roads other than those described above in the rural areas. They

form the basic road network within a Land Scherne or other sparsely populated

rural area. They also include roads with special functions such as holiday resort

roads, security roads or access roads to microwave stations. They serve

mainly local traffic with short trip lengths with no access control.

(b)

(c)

(d)

(e)


(0 ArterialsAn arterial is a continuous road within partial access control for through trafficwithin urban areas. Basically it conveys traffic from residential areas to thevicinity of the central business district or from one part of a city to another whichdoes not intend to penetrate the city centre. Anerials do not penetrate identifiableneighbourhoods. Smooth traffic flow is essential since it carries larse trafficvolumes.

CollectorsA collector road is a road with partial access control designed to serve as acollector or distributor of traffic between the arterial and the local road systems.Collectors are the major roads which penetrate and serve identifiableneighbourhoods, commercial areas and industrial areas.

Local Streets

The local street system is the basic road network within a neighbourhood andserves primarily to offer direct access to abutting land. They are links to thecollector road and thus serve short trip lengths. Through traffic should bediscouraged.

The characteristics for road categories are summarised as in Table 2-r.

TABLE 2.1 : CHARACTERISTICS OF ROAD CATEGORIES

(e)

(h)

AREAROAD

CATEGORIESTrip Length Design Volume Speed NETWORK

Long Med Short Hieh Med Low High Med Low

RURAL

Expressway I

-I National network

Highway

-

I I t I I National network

Primary Road I I I I E State networkSecondary Road I I !E * E - District network

Minor Road I IT

-Supporting network

URBAN

Expressway

-I E ! r National network

Arterial T IMajor links to

Urban centres

Collector E I E E - I Major streets within

urban centres

Local Street E E EMinor streets/town

network.


2.2 DESIGN STANDARDS FOR ROADS

2.2.1 The Importance of Standardisation

Technically, the geometric design of all roads need to be standardised for the following

reasons:-

(a) to provide uniformity in the design of roads according to their performance

requirements.

to provide consistent, safe and reliable road facilities for movement of traffic.

(c) to provide a guide for less subjective decision on road design.

2.2.2 Rural and Urban Areas

Urban areas are defined as roads within a gazetted Municipality limits or

township having a population of at least 10,000 where buildings and houses are gathered

and business activity is prevalent. Any roads outside the Municipality limits is

considered rural, including roads connecting Municipalities that are more than

5 kilometres apart.

There is no fundamental difference in the principles of design for rural and urban roads.

Roads in urban areas, however, are characterised by busy pedestrian activities and

frequent stopping of vehicles owing to short intersection spacings and congested built-up

areas. Lower design speeds are usually adopted for urban roads and different cross

sectional elements are applied to take into account the nature of traffic and adjoining land

use. It is for these reasons that variations in certain aspects of geometric design are

incorporated for these two broad groups of roads.

2.2.3 Application of Design Standards for Roads

The design standard is classified into six (6) groups (R6, R5, R4, R3, R2 & R1) for rural

(R) areas and into six (6) groups (U6, U5, U4,U3,U2 & Ul) for urban (U) areas. Each

of these standards are listed below with descending order of hierarchy.

(a) Standard R6/U6: Provides the highest geometric design standards for

rural or urban areas.They usually serve long trips

with high travelling speed (90 kph or higher)of

travelling,comfort and safety. It is always designed

with dividedcarriageways and with fuli access control.

The Rural and Urban Expressway falls under this

standard.

(b)

A Guide on Geomelric Design of Roads

(b) Standard R5/U5:

(c) Standard R4N4:

(d) Standard R3/U3:

(e) Standard R2N2:

(0 Standard R1/U1:

Provides high geometric standards and usually serve longto intermediate trip lengths with high ro mediumtravelling speeds (80 kph or higher). It is usually withpartial access control. The Highway, Primary Road and

Arterial fall under this standard. It is sometimes designedas divided carriageways with partial access control.

Provides medium geometric standards and serveintermediate trip lengths with medium travelling speeds(70 kph or higher). It is also usually with partial access

control. The Primary Road, Secondary Road, MinorArterial and Major Collector fall under this standard.

Provides low geometric standard and serves mainly localtraffic. There is partial or no access control. TheSecondary Road, Collector or Major Local Streets arewithin this standard. The travelling speed is usuallv60 kph.

Provides low geometric standards for two way flow.It is applied only to local traffic with low volumes ofcommercial traffic. The Minor Roads and Local Streets

fall under this standard. The travelling speed is usually50 kph.

Provides the lowest geometric standards and is applied toroad where the volumes of commercial vehicles are verylow in comparison to passenger traffic. The travellingspeed is 40 kph or less. In cases where commercial trafficis not envisaged such as private access road in low costhousing area, the geometry standards could be loweredespecially the lane width and gradient.

2.3 ACCESS CONTROL

2.3.1 Degree of Control

Access control is the condition where the right of owners or occupants of abutting landor other persons to access, in connection with a road is fully or partially controlled by thepublic authority.


Control of access is usually classified into three types for its degree of control, namelyfull control, partial control and non-control of access.

Full Control of Access means that preference is given to through traffic by providing

access connecting with selected public roads only and by prohibiting crossings at grade

or direct private driveway connections. The access connections with public roads varies

from 2 km in the highly developed central business area to 8 km or more in the sparsely

developed urban fringes.

Partial Control of Access means that preference is given to through traffic to a degree

that in addition to access connection with selected public roads, there may be some

crossings trafficked roads. At-grade intersections should be limited and only allowed at

selected locations. The spacin g of at-grade intersections preferably signalised may vary

from 0.4 km to 1.0 km.

To compensate for the limited access to fully or partially access controlled roads,

frontage or service roads are sometimes provided along side of the main roads.

In Non-Control Access, there is basically no limitation of access.

2.3.2 Selection of Access Control

The selection of the degree of control required is imporlant so as to preserve the as-built

capacity of the road as well as improve safety to all road users. Two aspects pertaining

to the degree of control is to be noted.

(a) during the time of design in the consideration of accesses to existing

develooments.

(b) after the completion of the road in the controi of accesses to futuredevelonments.

The selection of degree of access control depends on traffic volumes, function of the road

and the road network around the areas. Tables 2-2A and2-2F_ are general guides for the

selection of desree of access control.


TABLE 2-ZA: SELECTION OF ACCESS CONTROL (RURAL)

Xt'tn Standard

_____

Road categorr---'--R6 R5 R4 R3 R2 R1

Expressway

HighwayPrimary Road

Secondary Road

Minor Road

F

P

P P

P P

N N

TABLE 2-28: SELECTION OF ACCESS CONTROL (URBAN)

-----=pesign Standard\\\__r\\_

Road Category \-r'-\U6 U5 U4 U3 U2 U1

Expressway

ArterialCollectorLocal Street

F

P

P

P

P

N

P

N N N

Note : F = Full Control of Access,P = Partial Control of Access,N - No Control of Access

2.4 SELECTION OF DESIGN STANDARDS

2.4.1 Selection of Design Standard

The selection of the required design standard should begin with the assessment of thefunction of the proposed road and the area it traverses. If there is an overlapping offunctions, the ultimate function of the road shall be used for the selection criteria. Theprojected average daily traffic (ADT) at the end of the design life (15 years aftercompletion of the road) should then be calculated and from Table2-3, the requireddesign standard can be obtained. From the capacity analysis the required nurnber oflanes can then be calculated.


The selection of design standards used for various categories of roads is as

shown in Table 2-3 while the process of selecting design standard are as shown inFigure 2-I.

TABLE 2.3: SELECTION OF DESIGN STANDARD

Area\ Projected

\ ADTRoad \Category \

AllTrafficVolume

>10,000

10,000

to

3,000

3,000

to

1,000

1,000

to

150

< 150

RURAL

Expressway

HighwayPrimary Road

Secondary Road

Minor Road

R6

R5p< R4

R4 R3D' RI

URBANExpressway

ArterialsCollectorLocal Street

U6

U5

U5

U4U4U4

U3

U3 U2 U1


FIGURE 2-1 : FLOW CHART FOR SELECTION OF DESIGN STANDARDS

Project Identification

Designate Road GroupAccording to Nature ofArea Road Traverses

Select Road

Category based on

function e.g. Arterial

Select Road

Category based on

function e.g. Primary Road

Estimate ADT at

end of desisn life

Determine design

standard e.g. R6,U3 etc.

Route Location

Survey and Design

Table 2.3

r0

3.1


CHAPTER 3 - DESIGN CONTROL AND CRITERIA

This chapter discusses those characteristics that govern the various elements in the design ofhighway. These include the topography and land use through which the route is to be located,

the traffic that will use the route, design vehicles characteristics, design speed of the route and

the capacity to be provided along the route.

TOPOGRAPHY AND LAND USE

The location of a road and its design are considerably influenced by the topography,physical features, and land use of the area traversed. Geometric design elementssuch as alignment, gradients, sight distance and cross-section are directly affectedby the topography, and must be selected so that the road designed will reasonably fitinto those natural and man-made features and economise on construction and

maintenance.

The topography through which the road passes can generally be divided into threegroups, namely, FLAT, ROLLING and MOUNTAINOUS; where

FLAT terrain means: The topographical condition where highway sightdistances, as governed by both horizontal andvertical restrictions, are generally long or could be

made to be so without construction difficulty orexpertise. The natural ground cross slopes (i.e.,

perpendicular to natural ground contours) in a flatterrain are generally below 37o.

The topographical condition where the naturalslopes consistently rise above and fall below the

road or street grade and where occasional steep

slopes offer some restrictions to normal horizontaland vertical roadway alignment. The naturalground cross slopes in a rolling terrain are

generally between 37o-25%o.

The topogaphical condition where longitudinal and

transverse changes in the elevation of the ground

with respect to the road or street are abrupt and

where benching and side hill excavation are

frequently required to obtain acceptable horizontaland vertical alignment. The natural ground cross-

slopes in a mountainous terrain are generallyabove 25Vo.

ROLLING terrain means:

MOUNTAINOUS terTaln means:

11ll


The topography of a route may affect the operation characteristic of the roadway and thismay affect the type of road to be built. For example, steep gradient will reduce thecapacity of a2-Iane road (single carriageway) and lower the operation speed of this link.However, if a dual carriageway or a wider road is used, the effects will be much less andhence the operation speed and characteristics of the road will be enhanced. Consequently,the nature of the terrain sometimes determines the type of road to be built.

Topographical conditions may also affect the cross-sectional alrangement of dividedroads. In some cases a facility of a single road formation may be appropriate; in othersit may be more fitting to locate the road within two separate road formation due toeconomic or environmental considerations.

In urban areas, land development for residential, commercial and industrial purposes willrestrict choice of road location, lower running speed, generate more turning movements,and require more frequent intersections than in open rural areas. Geologic and climaticconditions must also be considered for the location and geometric design of a road.

3.2 TRAFFIC

The design of a road should be based on traffic data, which serve to establish the "loads"for geometric design. Traffic data for existing roads or section of road are available fromthe annual "Road Traffic Volume, Malaysia" published by Highway Planning Unit(HPU) of the Ministry of Works, Malaysia.

3.2.1 Average Daily Traffic (ADT)

ADT represents the total traffic for the year divided by 365, or the average traffic volumeper day. ADT is imporlant for purposes such as determining annual usage as justificationfor proposed expenditures, or for design of structural elements of a road. The projectedADT is also used to designate the standard of road as shown in Table 2.3 - Selection ofDesign Standards. However, the direct use of ADT in geometric design is not appropriatebecause it does not indicate the significant fluctuation in the traffic volume occurringduring various months of the year, days of the week or hours of the day. A moreappropriate measurement is the hourly volume which is used to determine the capacityrequirement of the road.

3.2.2 Design Hourly Volume (DHV)

The traffic pattern on any road shows considerable fluctuation in traffic volumes duringthe different hours of the day and in hourly volumes throughout the year. It is difficultto determine which of these hourly traffic volumes should be used for design. It wouldbe wasteful to base the design on the maximum peak hour traffic of the year, yet the useof the average hourly traffic would result in an inadequate design.

TZ


To determine the hourly traffic best fitted for design, a curve showing the variation inhourly traffic volume during the year is used. The hourly traffic used in design is the

30th. highest hourly volume of the year, abbreviated as 30 HV. The design hourlyvolume, abbreviated as DHV is the 30HV of the future year chosen for the design.

The above criteria is applicable to most rural and urban roads. However, for roads onwhich there is unusual or highly seasonal fluctuation in traffic flow such as holiday resortroads, the 30HV may not be appropriate. It may be desirable, to choose an hourly volumefor design (about 50 percent of the hourly volumes) expected to occur during a very fewmaximum hours (15 to 20) of the design year whether or not it is equal to 30HV.

3.2.3 Design Hourly Volume Ratio (K)

K is the traffic ratio of DHV to the designed ADT. K's value ranges froml%o to 20Vo. Theactual value should be obtained from traffic data or census. As a guide, K=12.0Vo forurban roads and K=15%o for rural roads may be used. Where the design of the road

facility is sensitive to the value of K, the K value should be established from trafficsurvey/study.

The directional distribution of traffic (D) during the design hour should be determinedby field measurements on the facilities. Generally D value of 60Vo can be used in urbanareas and 65Va in rural areas. Traffic distribution by directions is generally consistentfrom year to year and from day to day except on some roads serving holiday resort area.

3.2.4 Traffic Composition

This refers to the percentage of various classes of vehicles in the DHV. Vehicle ofdifferent sizes and weights have different operating characteristics which must be

considered in geometric design. Commercial vehicles generally are heavier, slower and

occupy more roadway space, thus imposing greater traffic effect on the road than

passenger vehicles"

Vehicles of various sizes and weights are classified into the following six (6) groupsunder the annual National Traffic Census conducted by HPU:a. motor cyclesb. cars and taxisc. light vans and utility vehiclesd. medium lorries (2 axle)e. heavy lorries (3 or more axles)f. buses

On existing road network, the traffic composition at peak hour can be established from"Road Traffic Volume Malaysia" published by the Highway Planning Unit, Ministry ofWorks.

3.2.5 Projection of Traffic

New roads or improvements of existing roads should be based on future traffic expected


to use the facilities. Desirably, a road should be designed to accommodate the traffic thatmight occur within the Iife of the facility under reasonable maintenance. l'he projectionof traffic for use in the design should be based on a period of l5 years after completionof the road

3.3

The geometric design of roads is affected by the physical characteristics of vehicles andthe proportions of various sizes vehicles using the roads. A design vehicle is a selectedmotor vehicle, the weight, dimensions and operating characteristics of which are used toestablish highway design controls to accommodate vehicles of a designated type. Forpurposes of geometric design, the design vehicle should be one with dimensions andminimum turning radius larger than thoie of almost all vehicles in its class. Since roadsare designed for future traffic, the sizes of vehicles used in the design should bedetermined by analysing the trends in vehicle dimensions and characteristics.

3.3.1 Design Vehicles

The design vehicles to be used for geometric design follows that used by AASHTo asin chapter II of AASHTo "Design vehicle" - -A policy of Geometric Design ofHighways and streets (1994). Figure 3-1,3-2,and 3-3 show the dimensions and turningcharacteristics for the p, SU and wB-r5 design vehicres.

3.3.2 Summary of Dimension of Design Vehicles

Table 3-1 below summarises the design vehicle dimensions and characteristics.

TABLE 3-I-DIMENSION OF DESIGN VBHICLES

Design Vehicles Dimension in Metres

Turning Radius(Metres)

InnerOuter

TypeEquivalent

Type inAASHTO

Wheelbase

Overhang

OverallLength

Overallwidrh Height

Front Rear

Passenger Car P 3.4 0.90 I.5

1.8

5.8 2.1 1.3 4.2 | --)

Rigid Truck SU 6. l0 1.2 9.1 2.60 4.10 8.5 12.8

Semi-Trailer wB-15 9. 10 0.9 0.60 16.1 2.60 4"10 5.8 13.7

Note: Marimum alIowable overall f"n(i) Rigid vehicle - 12.2 m &0 ft\(ii) Articutated vehicte _ 16.0 m (52.5 ft)(iii) Semi-Trailer - I 2.5 m &tft\(iv) Traiter - 9.0 m (29.5 fi)(v) Truck Trailer - 18.0 m (59 fr)

B. Maximum allowable overail width under currenf Maraysian Legisration is 2.5 m.

14

FIGURE 3.1 : P DESIGN VEHICLE

,/4 ,1t. | |/ry'

/ -///

//// / -/:A/ / .t(g$-L'//.'Y'//.-r.

/ / -'/ /'//..t.'

//,.t-'//.t/-

/ / ,t' -.'/ /z' -'/ .rf/-/'/ //' '\\ W-2

,' / ,/' ->.\-,i,r/'-Jix

\-r1?'-- l9x.--.--\

---.

r!\. --. \\rl tt. ----._ ---=-

it., tr. --.tS-

\-

''Q'.

r5

FIGURE 3.2 : SU DESIGN VEHICLE

//At f. l /

/' 60/,/ ,7v/.2/ '/ '-'4J,' // .t' {V.'

/' / -.rr' ,'//.t-'

/ ,/ .t /./'1,/.t// / /' '//' / -t ,.'/ -E-

,/,i17,?.ol',//_._._\ __

I,II

,YK,, t). \\r--.-I '\ -.-

- A*----.-{o.\

t,,\\ t'

f,"i_

369SCALE IN MFTERS

t6

FIGURE 3.3 : WB-ls DESIGN VEHICLE

//rf1 // /.6) /r e//t - / ..'

// i ."r19 "//rt\7/

ti.t.'/////i-"'//irtz'

./ / -z/ ,'.//.r// tz- .a

,y'i----'-=?:-- -----=-/'

f / ///;//

\'q >/

/\\// \.-__--,/ -_--\-{_/ --'-/,-\--/ -- \/-t\

.r' ,l!._r;-,- \'r' 5,s/ -\-- \-- 'ir

,l )#(.J*"" fl 'ti,..... -\--_ -\\\\I ,' -{u* c;l '\--'r i \ --- \f /" "r

------- q;-i t '\ '\ | r ---i,/ \. \. i \. --_:/ \ \ I \!/ \ \ I \l'r\.1\

\\.'",1 l\. 'rllt.\ \\\\\ ^\r (z\\\ \,4\ \\\

\

ffi0s6912SCALE IN MTTERS

l t 1

t7


3.4 SPEED

Speed is a primary factor in all modes of trahsportation, and is an important factor in thegeometric design of roads. The speed of vehicles on a road depends, in addition tocapabilities of the drivers and their vehicles, upon general conditions such as the physicalcharacteristics of the highway, the weather, the presence of other vehicles and the legalspeed limirations.

The speed is selected to meet the needs of the road to fulfil its function. Thus roads whichare planned to provide long distance travel will be designed with a higher speed whilethose which provides shorter distance travel can be given a lower design speed.

3.4.1 Design Speed

Table 3-2A and 3-28 indicate the selection of design speeds rvith respect to rural andurban standards.

Design speed is defined as: "a speed selected to establish specific minimum geometricdesign elements for a particular section of highway". These design elements includevertical and horizontal alignment, and sight distance. Other features such as widths ofpavement and shoulders, horizontal clearances, etc., are generally indirectly related todesign speed.

The choice of design speed is influenced primarily by factors such as the terrain,economic, environmental factors, type and anticipated volume of traffic, functionalclassification of the highway, and whether the area is rural or urban. A highway in levelor rolling terrain justifies a higher design speed than one in mountainous terrain.

Where a difficult location is obvious to approaching drivers, they are more apt to accepta lower design speed than where there is no apparent reason for it. Where it is necessaryto reduce design speed, many drivers may not perceive the lower speed condition ahead,and it is important that they be warned in advance. The changing conditions should beindicated by such traffic devices as speed zone signs and appropriate warning signsdepicting the conditions ahead.

A highway carrying a large volume of traffic may justify a higher design speed than aless important faciliti' in a similar topography, pafticularly where the savings in vehicleoperation and other cos.ts are sufficient to offset the increased cost of right of way andconstruction. On the contrary, a lower design speed should not be assumed for asecondary road where the topography is such that drivers are likely to travel at highspeeds.

Taking into account the above considerations, as high a design speed as feasible shouldbe used. It is preferable that the design speed for any section of highway be a constantvalue. However, during the detailed design phase of a project, special situations may

18


DesignStandard

Catesorv of Road

Design Speed (kph)

Terrain

Flat Rolling Mountainous

R6 Expressway 110 r00 80

R5HighwayPrimary Roads

100

r009090

'7n

70

R4Primary RoadsSecondary Roads

9090

80

80

6060

R3 Secondary Roads 80 60 50

R2Minor Roads

60 50 40

RI 50 50 30

TABLE 3-2A: DESIGN SPEED FOR RURAL ROADS

TABLE 3-2B-- : DESIGN SPEED FOR URBAN ROADS

DesignStandard

Category of Road

Design Speed (kph)

Area Type

I il m

U6 Expressway 100 90 80

U5ArterialsCollectors

9080

7010

6060

U4ArterialsCollectorsLocal Streets

801070

606060

505050

U3CollectorsLocal Streets

6060

5050

4040

U2UI

Local Streets5040

4A

30

3030

Note : Type I - relatively free in road location with very little problems as regards land

acquisition, affected buildings or other socially sensitive areas.

Type II - Intermediate between I and IILType III - Very restrictive in road location with probiems as regards land acquisition,

affected buildinss and other sensitive areas.

19


arise in which engineering, economic, environmental, or other considerations make itimpractical to provide the minimum elements established by the design speed. The mostlikely examples are partial or brief horizontal sight distance restrictions, such as thoseimposed by bridge rails, bridge columns, r'etaining walls, sound walls, cut slopes, andmedian barriers.

The cost to correct such restrictions may not be justified. Technically, this will result ina reduction in the effective design speed at the location in question. Such technicalreductions in design speed shall be discussed with and upprou"d by Road Authorities.

3.4.2 Operating Speed

Operating speed is the highest overall speed at which a driver can travel on a given roadunder favourable weather conditions and prevailing traffic conditions without at any timeexceeding the design speed on a section by section basis.

3,4.3 Design Sections

In the design of relatively long road, it is desirable, although not always feasible to allowfor a constant design speed. Changes in terrain and other physical controls may dictatea change in the design speed on certain sections. If a different design speed is introduced,the change should not be abrupt but should be effected over a ruffi.i"nt distance topermit drivers to change speed gradually before reaching the section of highway withlower design speed. There should be a transition section of at least I km per every t0 kphdrop in design speed to permit drivers to change speed gradually before reaching thesection of the road with a different design speed. The transition sections are sections withintermediate design speeds. Where the magnitude of the change in the design speed arelarge, more than one transition section will be required.

The intermediate design speed shall follow the sequence as established in Table 3-2Aand 3-28, i.e. If the design speed of section A is I l0 kph and that of section B is 90kph,then the design speed of the transition section between them shall be 100knh.

3.5 CAPACITY

The term highway capacity pertains to the ability of a roadway to accommodate rraffic.It is defined as the maximum number of vehicles that can pass over a given section of alane or a roadway during a given time period under prevailing roadway and trafficconditions. Capacity considered here is applicable only to uninterrupted flow or openroadway conditions. Capacity for intemrpted flow as at intersections will be dealt withseparately.

Capacity is often stated in terms of passenger car units (p.c.u). Table 3-3 gives theconversion factors to be used in converting the various classes of vehicles to passengercar units.

20

A Gui.de on Geometric Design of Roads

TABLE 3.3.CONVERSION FACTORS TO P.C.U.

Equivalcnt Value in P.C.U

Type of Vehicles Rural Standard Urban Standard Roundabout Design Traffic SignalDesign

Passenger Car 1.00 r.00 1.00 1.00

Motor cycles r.00 0.7.5 0.75 0.33

Light Vans 2.00 2.00 2.00 2.00

Medium Lorries 2.50 2.50 2.80 1.75

Heavy Lorries 3.00 3.00 2.80 2.25

Buses 3.00 3.00 2.80 2.25

Source : 1. Road Research Laboratory "Research on Road Traffic", HMSO, London, 1965, pp201

2. Highway Planning Unit, Ministry of Works, Malaysia

3.5.1 Capacity under ideal condition

Under ideal condition, the possible capacity for uninterrupted flow are as follows:

a. For 2-lane two way (total) = 2,800 pcu/hrb. For multi lane (per lane) = 2,000 pcu/hr

Ideal conditions consist of the following for two -lane roads:

a. Design speed greater than or equal to 100 kphb. Lane widths greater than or equal to 3.65m (i2')c. Clear shoulders wider than or equal to 1.83m (6')

d. No "No passing zones" on the highwaye. All passenger cars in the traffic streamsf. A 50/50 directional split of trafficg. No impedient to through traffic due to traffic control or turning vehiclesh. Level terrain

Where one or more of these conditions are not met, the actual capacity will be reduced.

The effects of each are discussed in the Highway Capacity Manual which gives

adjustment factors for the determination of the design capacity.

3.5.2 Design Volume

Design volume is the volume of traffic estimated to use the road during the design year,

which is taken as l5 years after the completion of the road. The derivation of the design

hour volume (DHV) is as discussed in Section 3.2.2.

2l

A Cui.de on Geometric Design of Roads

Design of new highways or improvements of existing highways usually should not be

based on current traffic volume alone. Considerations should be given to the future traffic

expected to use the facilities. A highway should be designed to accommodate the trafficthat might occur within the life of the facility under reasonable maintenance.

It is difficult to define the life of a highway because major segments may have differentlengths of physical life. Furthermore, the design of highway based on life expectancy is

greatly influenced by economics.

3.5.3 Service Volume

The service volume is the maximum volume of traffic that a designed road would be able

to serve without the degree of congestion falling below a preselected level as defined by

the level of service which is the operating conditions (freedom to manoeuvre) at the time

the traffic is at the design hour volume. Table 3-4 gives an indication of the levels ofservice used while Figure 3-4 gives a schematic concept of the relationship of level ofservice to operating speed and volume/capacity ratio.

TABLE 3-4 : LEVELS OF SERVICE

Level ofService

Remarks

A Free flow with low volumes, densities and high speeds. Drivers can

maintain their desired speeds with little or no delay.

B Stable flow. Operating speeds beginning to be restricted somewhat

by traffic conditions. Some slight delay.

C Stable flow. Speeds and manoeuvrability are more closely

controlled by higher volumes. Acceptable delay.

D Approaching unstable flow. Tolerable operating speeds which are

considerably affected by operating conditions. Tolerable delay.

E Unstable Flow. Yet lower operating speeds and perhaps stoppages

of momentary duration. Volumes are at or near capacity congestion

and intolerable delay.

F Forced Flow. Speeds and volume can drop to zero. Stoppages can

occur for long periods. Queues of vehicles backing up from a

restriction downstream.

22

FIGURE 3.4 : RELATIONSHIP OF LEI'EL OF SERVICE TO

OPERATING SPEED AIYD VOLUME iCAPACITY RATIO.

!t)!.)o.aoll

'.4oL0,oo

Volume / Copocity Rotio

z5


3.5.4 Design Level of Service and Volume/Capacity Ratio

The selection of the design level of serviqe is as given in Table 3-5A and 3-58. Thislevel of service concept can be simplified into volume to capacity ration (V/C) for thepurpose of design to determine the service volume as indicated in Section 3.5.3. Table3-5A and Table 3-58 also gives the ranges of V/C ratio consistent with the levels ofservice for the purpose of design.

TABLE 3-5A : DESIGN LEVEL OF SERVICE AND VOLUME/CAPACITY RATIO (RURAL)

Road Category Desisn Level of Service Volume /CapacityRatio

Expressway C 0.70-0.80

Highway C 0.70-0.80

Primary Road D 0.80-0.90

Secondary Road D 0.80-0.90

Minor Road E 0.90- 1.00

TABLE 3-58 : DESIGN LEVEL OF SERVICE AND VOLUME/CAFACITY RATIO (URBAN)

Road Category Desien Level of Service Volume /CapacityRatio

Expressway D 0.80-0.90

Arterial D 0.80-0.90

Collector D 0.80-0.90

Local Street E 0.90-1.00

.A


4.1

CHAPTER 4 - ELEMENTS OF DESIGN

SIGHT DISTANCE

4.1.1 General

Sight distance is the length of road ahead visible to drivers. Ability of a driverto see ahead is of the utmost importance to the safe and efficient operation of aroad. The designer must provide sight distance of sufficient length in which driverscan control the speed of the vehicles so as to avoid striking an unexpected obstacleon the travelled way. Also, at frequent intervals and for a substantial portionof the length, Z-lane undivided roads should have sufficient sight distance to enabledrivers to overtake vehicles without hazard. Decision sight distance, is the distancerequired for a driver to detect an unexpected hazard and to select an appropriatespeed or path thus by completing a manoeuvre which avoid this hazard. Sightdistance thus includes stopping sight distance, passing sight distance and decisionsight distance.

4.1.2 Stopping Sight Distance

The stopping sight distance is the length required to enable a vehicle travelling at or nearthe design speed to stop before reaching an object in its path. Minimum stopping sightdistance is the sum of two distance.

(i) the distance traversed by a vehicle from the instant the driver sights an object forwhich a stop is necessary, to the instant the brakes are applied; and

(ii) the distance required to stop the vehicle after the brake application begins.

(a) Perception and Brake Reaction Time

For safety, a reaction time that is sufficient for most operators, rather thanfor the average operator, is used in the determination of minimum sightdistance. A perception time value of 1.5 seconds and a brake reactiontime of a full second are assumed. This make the total perception and

brake reaction time to be 2.5 seconds.

(b) Braking Distance

The approxirnate braking distance of a vehicle on a level roadway isdetermined by the use of standard formula:

V2

254fd=

25


where d = brake distance, (m)

V= initial speed, (kph)f = coefficieirt of friction between tires and roadway

In this formula the f factor varies considerably due to many physical

elements such as condition of tires, condition of pavement surface, the

presence of moisture etc. The value of f for design are inclusive of all

these factors.

(c) Design Values

The sum of the distance traversed during perception and brake reaction

time and the distance required to stop the vehicle is the minimum

stopping sight distance. The values to be used for minimum stopping

sight distances are as shown in Table 4-1.

TABLE 4.1 : MINIMUM STOPPING DISTANCE

Effect of Grades on Stopping Sight Distance

When a road is on a grade the standard formula for braking distance is

V2D_ zsatl,e)

in which g is the percentage of grade divided by 100.

The effect of grade on stopping sight distance is as shown in Table 4-2.

(d)

Min Stopping Sight Dist. (m)Design Speed (kph)

110

r009080t060504030

2s0205r70t40110

85

65A<AJ

30

1A


(e)

(f)

TABLE 4.2 : EFFECTS OF GRADES IN STOPPING SIGHTDISTANCE _ WET CONDITIONS

Every effort should be made to provide stopping distances greater than

the minimum design values shown in Table 4-1 especially at locationswhere there are restrictions to sight in the horizontal plane.

Decision Sight Distance

Stopping sight distances are usually sufficient to allow reasonablycompetent and alert drivers to come to a hurried stop under ordinarycircumstances. However, these distances are often inadequate when

drivers must make complex or instantaneous decisions, when informationis difficult to perceive, or when unexpected or unusual manoeuvres are

required. Limiting sight distances to those provided for stopping may

also prelude drivers from performing evasive manoeuvres, which are

often less hazardous and otherwise preferable to stopping. Even with an

appropriate complement of standard traffic control devices, stopping sightdistances may not provide sufficient visibility distances for drivers tocorroborate advance warning and to perform the necessary manoeuvres.It is evident that there are many locations where it would be prudent toprovide longer sight distances. In these circumstances, decision sightdistance provides the greater length that drivers need.

Decision sight distance is the distance required for a driver to detect an

uriexpected or otherwise difficult-perceive information source or hazard

in a roadway environment that may be visually cluttered, recognise the

hazard or its potential threat, select an appropriate speed and path, and

initiate and complete the required safety manoeuvre safely and efficiently.Because decision sight distance gives drivers additional margin for errorand affords thern sufficient length to manoeuvre their vehicles at the same

or reduced speed rather than to just stop. its values are substantiallygrcater than stupping sight distance.

DesignSpeed (kph)

Stopping SightDistance (m) for

Downgrades

AssumedSpeed forCondition

(koh)

Stopping SightDistance (m) for

Upgrades37a 6Vo 97o 3Vo 6Vo 9Vo

3040506070

8090100

110

30466689118

149181

221

267

3l4869

94126161

t95241293

)L50'73

101

136

t76714261327

30404755

637071

85

91

29+J5671

90t071aAlLa

148

r68

2942546986102119140159

)9,

41

5Z6183

981taI lJ

t34l5i

21


Drivers need decision sight distance whenever there is a likelihood forerror in either information reception, decision-making, or control actions.The following are examples of critical locations where these kinds oferrors are likely to occur, and where it is desirable to provide decisionsight distance: interchange and intersection locations where unusual orunexpected manoeuvres are required; and changes in cross section such

as toll plaza and lane drops.

The decision sight distances in Table 4-3 provide values to be used bydesigners for appropriate sight distances at critical locations and serve as

criteria in evaluating the suitability of the sight lengths at these locations.Because of the additional safety and manoeuvrability these lengths yield,it is recommended that decision sight distances be provided at criticalIocations or that these points be relocated to locations where decisionsight distances are available. If it is not possible to provide thesedistances because of horizontal or veftical curvature or if relocation is notpossible, special attention should be given to the use of suitable trafficcontrol devices for providing advance warning of the conditions that arelikely to be encountered.

TABLE 4-3 : DECISION SIGHT DISTANCE

DesignSpeed (kph)

Decision Sight Distance for AvoidanceManoeuvre (meters)

B C D

5060708090r00ll0

15

95125155

i85225

26s

160

20s250300360415,,t<<

145

115200230215

3r5335

200235215315

360405

42s

Decision sight distance values that will be applicable to most situationshave been developed from empirical data. The decision sight distancesvary depending on whether the location is on a rural or urban road, andon the type of manoeuvre required to avoid hazards and negotiate thelocation properly. Table 4-3 shows decision sight distance values forvarious situations rounded for design. As can be seen in Table 4-3,generally shorter distances are required for rural roads and when a stopis the manoeuvre involved.

28

A Gui.de on Geometric Design of Roads

The following avoidance manoeuvres are covered in Table 4-3:. Avoidance Manoeuvre A : Stop on rural road.. Avoidance Manoeuvre B : Stop on urban road.. Avoidance Manoeuvre C : Speed/path/direction change on rural

road.. Avoidance Manoeuvre D : Speed/path/direction change on urban

road.

In computing and measuring decision sight distances, the 1070mm eyeheight and 150mm object height criteria used for stopping sight distancehave been adopted. Although drivers may have to be able to see the

entire roadway situation, including the road surface, the rationale for the

150mm object height is as applicable for decision as it is for stopping

sight distance.

4.1.3 Passing Sight Distance

Most roads in rural areas are two-lane two way on which vehicles frequently overtakeslower moving vehicles, the passing of which must be accomplished on a lane regularlyused by the opposing traffic. Passing sight distance for use in design should be

determined on the basis of the length needed to safely complete a normal passing

manoeuvre.

The minimum passing sight distance for two-lane highways is determined as the sum offour distances:-

(i) distance traversed during the perception and reaction time and during the initialacceleration to the point of encroachment on the passing lane.

(ii) distance travelled while the passing vehicle occupies the passing lane. ,

(iii) distance between the passing vehicle at the end of its manoeuvre and the oppositevehicles.

(iv) distance traversed by an opposing vehicle for two-thirds of the time the passing

vehicle occupies the passing lane.

(a) Design Values

The total passing sight distance is determined by the sum of the above fourelement" Table 4-4 gives the minimum values to be used for each design speed.

In designing a road, these distances should be exceeded as much as practicableand such sections provided as often many as can be done with reasonable costs

so as to present as many passing opportunities as possible exceeded.

29


I

I

III

I

i

TABLE 4-4 : MINIMUM PASSING SIGHT DISTANCES(2-LANE - 2 WAY)

Design Speed (kph) Minimum Passing Sight Dist. (m)

110

100

90807060504030

730610610550490410350290230

Effect of Grade on Passing Sight Distance

Specific adjustment for design use is not available. The effect of grade is notconsidered in design as the effect is compensated in upgrade or downgrade.However, it should be realised that greater distances are needed for passing ongrade as compared to level conditions. The designer should recognise thedesirability of increasing the minimum as shown in Table 4.4.

Frequency and length of Passing Sections

Sight distance adequate for passing should be provided frequently on 2-laneroads. Designs with only minimum sight distance will not assure that safepassing can always be made. Even on low volume roads a driver desiring to pass

may, upon reaching the section, find vehicles in the opposing lane and thus beunable to utilise the section or at least not be able to begin to pass at once.

The percentage of length of road or section of road with sight distance Ereaterthan the passing minimum should be computed. The adequacy of sight distanceis determined by analysis of capacity related to this percentage, and this wouldindicate or not alignment and profile adjustments are necessary to accommodatethe design hour volumes. Generally this percentage should be about 60Vo for flatterrain, 40Vo for rolling terrain and 20Vo for mountainous terrain. The avaiiablepassing sight distances should not be concentrated in one section but be evenlydistributed throughout the entire road. It is inrportant to note that in order to caterfor high volume of traffic at high level of service, it requires that frequent andnearly continuous passing sight distances be provided.

(b)

(c)

30

T

A Guide on Geometic Design of Roads

4.1.4

It is not necessary to consider passing sight distance on roads that have

two or more traffic lanes in each direction of travel. Passing manoeuvres

on multilane roads are expected to occur within the limits of each

carriageway allocated for that direction of travel. Thus passing manoeuvres

that require crossing the centerline of four-lane undividual road are reckless

and should be prohibited.

Criteria for Measuring Sight Distance

(a) Height of Driver's Eye

The eyes of the average driver in a passenger vehicle are considered to be

l070mm above the road surface.

(b) Height of Object

A height of object of 150mm is assumed for measuring stopping sight distance

and the height of object for passing sight distance is 1300mm both measured fromthe road surface.

Sight distance should be considered in the preliminary stages of design when both

the horizontal and vertical alignment are still subject to adjustment. The sightdistance should be determined graphically on the alignment plans and recorded

at frequent intervals, for both direction of travel. This will enable the designer

to appraise the overall layout and effect a more balanced design by minoradjustments in the plan or profile.

Horizontal sight distance should be measured in the inside of a curve at the center

of the inside lane. Vertical sight distance should be measured along the

longitudinal profile of the central line, using the height of driver's eye (1070mm)

and the object height (150mm). Figure 4-l and 4-2 provrde examples ofmeasuring sight distance in both plan and profile respectively. For two lane two-way roads passing sight distance in addition to stopping sight distance and

decision sight distance should be measured and recorded. Sight distances, in this

case, are to be checked from the centerline of the road.

JI

zF]

-zrdUzFi(n

FFH

rarizEx30T

E

Qtrl&rlt

v27l-IDFF(t)

!-- t-Y**9.dt/jolL

*4lF<

--u) l)Hfixzt</^ t-vuDs] xF;9lltt.tx

(.)zFU)

F

v)

FI&

i;d=xacNvIsIo

t4

&;)(')

'JFzN&ra.r

ltl \

e\'dl\

ti'.6

32

. :-,J,

?'II

I

HF]tro&F{zoHOztsoFIAF

Fl+(ra((Jtiagz|<&paFIE

{$r.l&-rh\J|<fr

F

tsFtdtr

F

H

F

*llrqtr>-

?,

VE1Ji

F

v)arI1

F

rqFltl&Frl.l

OF&F]

33


4.2 HORIZONTAL ALIGNMENT

4.2.1 General

In the design of horizontal curves, it is necessary to establish the proper relation between thedesign speed and curvature and also their joint relations with superelevation and sidefriction. From research and experience, limiting values have been established for thesuperelevation (e), and the coefficient of friction (fl.

4.2.2 Superelevation Rates

The maximum rates of superelevation usable are controlled by several factors such asclimatic conditions, terrain conditions and frequency of very slow moving vehicles thatwould be subjected to uncertain operation. While it is acknowledged that a range of valuesshould be used, for practical purposes in establishing the design criteria for horizontalalignment, a maximum superelevation rate of 0.10 is used for roads in rural areas and 0.06for roads in urban areas.

4.2.3 Minimum Radius

The minimum radius is a limiting value of curvature for a given speed and is determinedfrom the maximum rate of superelevation and the maximum allowable side friction factor.

The minimum safe radius (Rmin) can be calculated from the standard curve formula.

Rmin = 127 (e+f)

WhereRmin = minimum radius of circular curve (m)

V = Design Speed (kph)

e = maximum superelevation rate

f = maximum allowable side friction factor

v2

34

4 Guile on Geometric Design of Roads

Figure 4-3 illustrates the range of side friction factors (0 that has been derived using

imperial methods for the various types of roads.

ion between t

,ation and si

blished for r,

FIGURE 4-3 : COMPARISON OF SIDE FRICTIONFACTORS ASSUMED FOR DESIGN OF

DIFFERENT TYPES OF ROADS

0.5

Maximum side friclion ./lactor tor new tyres on /wet concrete pavement

]-f 1l

Assum ed for designof turning roadways

concrete p

I

I

I

lyres on slvement

el

r..Assumed for design of

1/ tow speed urban roadsff

f--t ruraland high speedurban highways

A 0.4

actors SUCh r ;g vehicles th H'ange of valu, E u'r

for horizont 5areas and 0.( E

! O)

q)

(a

0.1

is determinekiction facto

formula.

U 30 40 50 60 70 80 90 100 I l0

Speed (kph)

Table 4-5 lists the minimum radius to be used for the designated speed and maximum

superelevation rates.

TABLE 4.5: MINIMUM RADIUS

Design Speed (kph) Minimum Radius (m)

e = 0.06 e = 0.10

110

100

90807060504A

30

s60465335284195

150

100

6035

s00315305230n512585

5030

35


While the values in Table 4-5 lists the minimum radius that can be used, it should be noted,that the above minimum radii will not provide the required stopping sight distance andpassing site distance within typical cross-sections. Hence, all elforti should be made todesign the horizontal curves with radii larger than the minimum values shown for greatercomfort and safety.

4.2.4 Transition (Spirat) Curves

Vehicles follow a transition path as it enters or leave a circular horizontal curye. To designa road with builrin safety, the alignment should be such that a driver travelling at the designspeed will not only find it possible to confine his vehicle to the occupied lane but will beencouraged to do so. Spiral transition curves are used for this purpose. Generally, theEulers spiral, also known as the clothoid is used. The degree of curve varies from zero atthe tangent end of the spiral to the degree of the circular arc at the circular curve end.

a) Length of Spiral

The length of spirals to be used are normally calculated from the Spiral formula orfrom the empirical superelevation runoff lengths. The following formula is used bysome for calculating the minimum length of a spiral:

, 0.0702v'L= RC

.,'where L = minimum length of spiral;

V - speed (kph);

R = curvo radius; and

C = rate of increase of centripetal accelerating (m/sec3)

The factor C is an imperial value and a range of lto 3 have been used for highways.Highways design does not normally require the level of precision achieved using thisformula. A more practical control for determining the length of a spiral is that *fri.ttequal the length required for superelevation runoff.

Superelevation runoff is the general term denoting the length of highway neededto accomplish the change in cross slope from a section with adverse crownremoved to a fully superelevated sectjon or vice versa. Current practice indicatesthat the appearance aspect of superelevation runoff largely governs the length.The length of superelevation runoff should not exceed a longitudinal slopeas indicated in Table 4-6.

36


TABLE 4.6: RELATIONSHIP OF DESIGN SPEED TO MAXIMUMRELATIVE PROFILE GRADIENTS

Table 4-74 and 4-78 gives for the various design speeds and degree of curvature,the minimum lengths of spiral, the superelevation rates and the limiting curvaturefor which superelevation is not required.

For pavements with more than 2 lanes and standard lane width of 3.5m, the

superelevation runoff lengths should be as follows.

(i) 3 lane pavements - 1.2 times the length for 2-lane roads.

(ii) 4?aneundivided pavements - 1.5 times the length for 2 lane roads.

(iii) 6 lane undivided pavements * 2.0 times the length for 2 lane roads.

Design Speedv (kph)

Maximum Relative Gradients (and EquivalentMaximum Relative Slopes)

for Profiles between the Edge of Two-LaneTravelled Way and the Centerline (Vo)

30405060708090100

110

0.75 (l:133)0.70 (l:143)0.65 (l:150)0.60 (1:167)0.55 (l:182)0.50 (1:200)0.48 (l:210)0.45 (I:222)0.42 (l:238)

37

,i

@c.)

@o6

,78FA

6 ;r

!o

>"Ocg! 0lO 6i iE.c o: i.c, EdL;O'X tr-o

^ v-.F

^

E E e E 3 gs I9.Yq.Y9?.? =rE o E 6:; o

",F-i€v'92 u ;:fE'fsuI* EisQezz.6t E

;; f q -:* i -Buo."'=-9-O-atr=.F q<Fl '= -g

o ? i ".= H Y.= H ==e 6 a = + E a.! i b.{XrE'E9s,PB .cvLrv!r!Fv*a

ililll ilIilil Etli

xox vvSe>il)ze

"!

olqJ

,. *avo\

F')

tl

^^clNC\dNNN(\N(\:9Su i cl. o\ o o\ cl. o\ o. o, o o. = '_ _

g

;o o 6.o ro \o \o \o \o lo \o \o b r- m

UU-!'.--:-:qqq-q-?qqZ Z -t..t o .i- <- .i- n n \o r @ C'' o'

yv

=J 2

il

-a.t 6a

oos$*$s$ss$sssE:OOH3H333HHH33SFFU U U d r-. vl oC q f] - @ c! c € o' €ZZE, ^i oi r; d; + + -; r; 'o.o rt od oi

ll

-J

.rE,l

ct 6a

o\

;

o(DOppPPPPFPFFFBg:

ooofiB3833333f;8FEF

U U U O.'i q ': .1 q'1 9 -: oq v] \q oq

zzz QZ ot c't..r o 6 V rf, n n \o r €

t--c'l

€ll

-l

o1 q

o,) 6e

ooooS€3€€€€€€39;FP

oooo$$*S+S$+S$Sfl€R

2222HXXK3:3ST::i3i

d

o*a-

-l

c{q!

o6Q

^ ^ o. o o. o' o o o\ o o\ o' -J !-- q $ rOO a U I h n !n Vt n n n h r) n \O F- € O. O'

^ ^ O\ O\ o\ O. O. O\ O\ o. o' O\ -: .-- J:. r. r,ou u e e 6 o o o 6 - ci - -- $ r. n \C \C

u o u o u o 1 c.t s q i n q n c'l a oc \ q qZ ZZZ Z & N c.r ct c.-l .i ci $ $ n \O a- € o\ o\

tl

d

it

;N!i

!

vo\

oooooo3S3383338 3 F 3 F R g Dg8

coooooRgSSnggSS n n + +S fi f AB

u u u u u u u u u cl vl \ -1 9 cl Q c'l - q "q J 9 =

:Z Z ZZ Z z e e e oi oi c't o s $ r, \o t- € oo o'\ o\ c\ :

II

.F

$q!

.rEr!

c.: 6a

tl

N o{ t\ cj ql qt ql c.l n c'r € 6 \S o-\ * S f- O *+ + + + + -t $ d d ri n ro \o \o F F- r- Ft @

€ oO € € cg og A oq I 6 m'"1 $ \O 6 O\ - m tueeeee &&c.fNalNc.telomm+$+.fSnnn

UUQUUUUUU r)r)r)-r- - € € \o \o - €': noq - vlo9QzzzzzzzzzY,Y,Y,.i l-i ; ; + ; J ; ; € # 6 c' ci c' 9

a-il

'J

,l

c-:6Q

6lii\tll

OOOOOOOOOOOOSSg g g8 g+€Silf, FA€ERFF

al N c .! ct c\ q'i \o o N c' s \o 6 q qr < F- o\ -N N N N N N'( Fi m ri o - -' +'f $ <- <+ rt

uuu u u u u u u u u u qq "1 oe q q o \o N I \ q a \ c'l : : :3ZZZZZZZZZZZZ&&^ini ri *r; r; tod'or-rF-€€oo\=

$tl

-J

NllFJ

o6Q

lzor_ltl

oooooooooooooooR R R RF R ESS E?Sg I 3fl € F

OOOOOOOOO OOOOOO : 5 : I : 9 K3]R S 3K; 3 3S $ S

uuuuuuuuuuu g!J99 9 "l 9 -. n o mn€ - nq-q o' nl :: 1Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z o' c't'-'r -i d + + + + r' vi n \D \c c- € c' c\

=====F F F K R ! =

: S =

A ; F 6 E v ;- ii'< :- - - - -

c{il

E&

,l

,zL/

,1

l-1azria

;F-

I$

.t

3

s

o6

EE

t

F

ao'Fo"'c:;

o-6>'I */r'vaL O .,)=-

cd j>

1r d.g F

!cFcitE:i o * o 7,9-=*F:i5rj-q->Eo",'<do ii,,9 ;, - h z o>.:'u =E:t ui_uE-q:;:tr

L-=tris",.=at."'-=Zyi-= EE E S

'F =?P C * : 5 i 8 illllllllltltll

UUaJZ&c--&>

Nt

;

^ ^ -$ -t <t.t Fi $ < v'f -{. $'t rtev6666mm€a@66r@

^ ^ \O \O \O \O .c) \O \O \.o \O \.o .O,D \O'vnnnnnr)nnrrrlr)nr)

u u u u vl ---.1 v-1 \ c.l ! q q 9 qZ Z & C( c.t o o o o'i- -$ -f n q n

n'tl

+q

R-"r E

il

ot$

nnnnnr,6nnr.nr)r)rrrrrrrrrrF-rF-

nnnnnnnr)nnr)nn

UUOU":F:ceqclqqqqqnqZZZ ol c.t c.l ol o - m m \i d n \a n

E,F

&

C) tsJ@

II

<-q

crq

o6R

+++++$st'-occ++++++++++++\i+

u u u u u c] 9 v? \ -: R g q .l oq.1 q qZZ Z Z & a^ N N m n -. v .1- v n r, \o

cnll

c./.

rtl

-J

crq,-..1

^ ^ cF. O cF or, cr ct\ c| c|\c|. cD O\ C O crv " n n n n n r) r) r) n 6 n v) v') vl

* .- o tt -, -, -, -, n -, -, -. -.

(-r (/ (/ U U U U -:.'j 9 c! - $. oq ^l r.ZZZZZdAzNc..INN-om$v

lnlo\l:cr\ c|\ o.l rl

lq

nn\ol

vt

.J

dq

o5l U U U O U U U U U --- cl vt c9 - vl q 9 q r] oC q qZZZZZZZ & & c{ c! cn ci 6 o <. s r, r, wr n \o

^cooocaooooocclorfUUUUUe?nnnnnn!^)n n nn !-) n nn

^o-mooo.i€oomonn\o999uueu- o moo-)-o m o o 6 o oo'vE

-J

ciq

or 6a

:l

II

cl al cn ci c'.1 cl c.l N cl al (.l m $ V) \O t- € O\eee $<.<-'f .f +-J..i-.f .f .f <-.f \j-$rt.f \.'

@ 6 @ oO oO € € oO € € € O. o.. O * * C'l Clol c.l ol N o.l c.l a] c.l cl ct c.l N ol o o o o o

UU UUU UU O (J U UU - 9 09.1 q cl \ q -]n 9 \oCqqZZZZZZZZZ & & &N N cr o - $ :i- n rr n n n n rt \o

il

tr

+E.J

.iq!

o5l

etr

t

m-- -, n - - m $ n \o r q ary - n \o.' ! u - 6 - o o - - - - - m -, f, \i $ < <- -i-

N N N ci N ^! cl N m m $ vl9 F: oC O O -u u u e u v e v v J u 9 N N Cl Ot Ot N 6l N 61 N -J ol a.l N N N - -

r) r) r ) r) tr rr tJ (J ( J (l t) r, r, () - n -

() o\ - s n \c m o N $ \o @ oZZZ ZZZ Z Z Z Z ZZ04 0a N ci m o o {- 'r. t+ $ .t n n v) n n \o

II

.F

&

-l

crqJ

o5R

\o \o \o \o \c .o \c I r m o o N < I q rl "?uuueueeeu c.tNNct(\olNa.lc\|.l616m---,vs

ooooooooooooooo=:::=!: ==9RRRKXFKRi

vU U U U U U U U U U U U U U U U U "1 Cq q'T N 9 O? Q -'1 N T: q -q O? qZZZZZZZZZZZZZZZ & & a cl -, - - - on $ <t v <- n n o €

.F

J)\Y 'vS== 9??=? a ? o eaaa a a a o n oq c c.c Q :?rn.f_N_o6(dcF6ri<;4--onond-N---rnmNN* :o'€r-'\on$€'l'i--

-_lI

I

I

I

II

I

II

I

I

II

I;lol6l:lOIbol'=l

IOI6l

:lOI

0lI'cl

zlFI

Iol=t

z

I

Fz2

0zr l't

a

F-I!$

F

h$r>a$'q

l-1 qaO\O\

n'+o

Fii


4.2.5 Methods of Attaining Superelevation

Three specific methods of profile design in attaining superelevation are (a) revolving the

pavement about the centreline profile (b) revolving the pavement about the inside edge

profile, and (c) revolving the pavement about the outside edge profile. Figure 4-4 illustrates

these three methods diagrammatically. The rate of cross slope is proportional to the distance

from start of superelevation runoff.

(a) Figure 4-4A illustrates the method where the pavement section is revolved about the

centreline profile. This general method is the most widely used in design since the

required .hung" in elevation of edge of pavement is rnade with less distortion then

by the other methods. The centreline profile is the base line and one-half of the

required elevation change is made at each edge'

(b) Figure 4-48 illustrates the method where the pavement section is revolved about the

inside edge profile. The inside edge profile is determined as the line parallel to the

calculateJ centreline profile, One half of the required change in cross slope is made

by raising the centre line profile with respect to the inside pavement edge and the

other half by raising the respect to the centreline profile.

(c) Figure 4-4C illustrates the method where the pavement section is revolved about

outside edge profile involves similar geometrics as (b), except that the change is

affected below the upper control profile.

Except when site condition specifically requires, method (a) shall be adopted for undivided

roads.

4.2.6 Superelevation Runoff with Medians

In the design of divided roads, the inclusion of a median in the cross section alters somewhat

the superelevation runoff treatment, The three general cases for superelevation runoff

design are as follows:

(a) The whole of the travelled way, including the median, is superelevated as a plane

section. This case is limited to namow medians and moderate superelevation rates

to avoid substantial differences in elevation of the extreme pavement edges because

of the median tilt. Diagrammatic profile controls is sirnilar to Figure 4'4a^ except' that the two rnedian edges will appear as profiles only slightly removed from

centreline.

(b) The medial is lield in a horizontal plane and the two pavements separately are

rotated around the median edges. This case has most application with medians of

intermediate width. Runoff design uses the median edge profile as the control' One

pavement is rotated about its lower edge and the other about its higher edge. The

diagrammatic profile control is similar to Figure 4-48 and 4'4C with the centreline

grade control the same for the two pavements.

40

-_

aAF{

rtrli(Ff-lEra

z>z'^A( )v*FHEa1n>|{ frlHJFt;itrFi's P,\J-*nAF(

---waEi .7^F\/<ztsr FrazE?,{ -\-J t-xtrl ru)4<-r-l Ff'^A-y

;I

$r-ltv.

rhfv.

E.ra\t)\\̂' td

\l;'. ! !:.)\lP\1fi)'E\lo p

'.4-a\ r B"r\l:z

.\ c 6:lnO

\ I-}!\ -l uL., .l 5Zh| <xl,lr>.l .; 66'lcz| ' <-{qHo

tJf

I vv)ltZa?? <<| ,:iI'H

,Faavlt z

I

zF7f

^=

Jv>

F2EJ

ca>

<:

2F7t ..,3 A8I F9 Ekt 6s.Bl Xrfi3 s EEl 4HE a "!Fl 3iH E i{ 85;i F'3q n;5 Erir "'i .-,Z 3l e BIHS d;F ft; Fi< sht: aEE 'ud Erd F,FYAEl Al- t 'l . / rrt''h r li ._1 /, -2:lll rJ2 F lr I I z

)-tl

"F Z ll 't I nff? d tt'l | <

^;-ltOE 6 l,'r rr)E Et tl.i , iF!:l ,, I l_uo"x zl ,t,t I -a7 t _jtif- IL< I l'll F

F I lrl ./ -goE *_ -'1;- 1-tr>3Fr6|t<<: Y,z , H {--"1s ?1? / 't \ e-LJll

rl :l<t7JIF rlxlg I

z1 o

Ltl

+l

Y

A Guiile on Geometric Design of Roads

(c) The two pavements are separately treated for run-off with a resultant variable

difference in elevation at the median edges. The differences in elevation of the

extreme pavement edges are minimised by a compensating slope across tlie median'

A fairly wide section is necessary to develop right shoulder areas and desired gentle

slope between. Thus this case is more applicable to wide median of 9m or more'

The pavement rotation can be made by any methods in Figure 4-4.

4.2.7 Pavement Widening on Curves

Pavements on curves are widened to make operating conditions on curve comparable to

those on tangents. Pavement widening on curves is the difference in pavement width

required on a curve and that use in a tangent. Table 4-8 gives the widths of pavement

widening that are required on open road curves.

Widening should be attained gradually on the approaches to the curve to ensure a reasonable

smooth alignment on the edge of pavement and to fit the paths of vehicles entering or

leaving the curve. Preferably, widening should be attained over the superelevation runoff

length with most of all of the widening attained at the start of circular curve poin

4,2.8 Sight Distance on Horizontal Curves

Another element of horizontal alignment is the sight distance across the inside of curves.

Where there are sight obstructions (such as walls, cut slopes, buildings and guardrails), a

design to provide adequate sight distance may require adjustment if the obstruction cannot

be removed. Using the design speed and a selected sight distance as a control, the designer

should check the actual condition and make the necessary adjustment in the manner most

fitting to provide adequate sight distance.

4,2.9 General Controls for Horizontal Alignment

In addition to the specific design elements for horizontal alignment, a number of general

controls ur".".ognised and should be used. These controls are not subject to empirical or

formula derivation but are important for the attainment of safe and smooth-flowing roads.

These are:-

(a) The horizontal alignment should be consistent with the topography and width

preserving developed properties and community values. Winding alignment

Lo*posed of short curves should be avoided. On the other hand very long straights

should also be avoided. The maximum length of straight section of the highway

should be limited, where possible, to 2 minutes travelling time.

ft) The use of the minimum radius for the particular design speed should be avoided

wherever possible. Generally flat curves should be used, retaining the maximum

curvature for the most critical conditions.

(c) Consistent alignment should always be sought. Sharp curves should not be

introduced at thd end of long tangents. Where sharp curves must be introduced, it

should be approached, where possible, by successively sharper curves from the

generally flat curvature.

42

c.):+

rbo

e€5Ht

o

zr q vl \

N

N nl

t--n.ro\ nl

nalF- nl \o nl

(\n

o{ nlt&

$

@

NIn\ooonl\o,

ol

NI

no\o*c{nlt& o' nl

,.t--9nr F- nl F- nl-&

m V)

co nlt&

'+

6o"F- nl9*.

o-Noz

,\m\O nlaN'

n\oQ^,

€€ n€€nl*& "d

o-V)nld

o--dnt €nl

f-

6Nnlil

canln\o\onl*&

n\o+nl\o*

€c.lNI*

O-€nl

nl O.$ nl-o(

o-@nl

oo

f-< -clFnr

ooN

oO

(/)

0)

o

o'lz&

a

r\

z

zrlizz

FFz

;I!+

'.\

E'i

. -,,"t

T.'r

A Cuide on Geontetric l)esign ttf Roads

For small deflection angles, curves shcluld be su{'f iciently long to avoid the

appearance o1'a kink. Curves should be at least l-50m long for a central angle of5o anci the length should be increased 30m foreach ludecrease in the centreline

angle. The n-rinin-rurn length clf horizontal curve on main roads, should be about

3 times the <iesign speed, L.,,ri,, = 3y (iri n-retef). on high speed controlled access

f acilities the desirable minirrum length of horizontal cun,e should be double the

minimum length i.e. [-.,j", = 6V.

(e) Any abrupt reversal in alignment should be avoided. The distance between

reverse curves shoulcl be the sum o1-the superelevation runofl'lengths and the

tangent runout lengths.

(f) The 'broken back' an'angentent of curves should be avoided. Use of spiral

transitions or a compound curve alignment is prelerable for such conditions if itis unavoidable.

(g) other than tangent or flat curvature should be avoided <-in high, long embankment

fills. In the absence of'cut slopes, shrubs, and tree above the roadway, it is

difficult fbr drivers to perceive the extent of curvature and adjust their operation

to the conditions.

(h) Caution should be exercised in the use of compound circular curves. While the

use of compound curves affords flexibility in fitting the highway to the terrain

and other ground controls, the simplicity with which such curves can be used

clften ternpts the <iesigner to use them without restraint. Preferably their use

should be avoided where curves are sharp. Cornpound curves with large

differences in curvature introduce the same problems that arise at a tangent

approach to a circular curve. Where topography or right-of-way restriction make

their use necessary, the radius of the flatter circular arc, R1, should not be more

than 50 percent greater than the radius of the sharper circuiar arc, R2, i.e., R1

should not exceed i,5 Rz. A several-step compound curve on this basis is

suitable as a fornt of transiticln to sharp curves. A spiral transitiott between flatcurves and sharp curves is even inore desirable. On one-rvay roads such as

rarnps, the dil rence in radii of compound curves is not so ituporiant if the

second curve is flatter than the first. However, the use of compound curves on

ramps. which results in a flat curve between two sharper curves, is not good

practice.

(i) The designer should ensure thaL the required sight distance (i.e. decision sight

ciistance) is providecl when approaching interchanges and intersections'

4"3 \/ERTICAL AI,IGNMF'NT

4.3.1 Maximum Grades

The vertical profile of road affect tlie perfomrance of vehicles. The effect of grades on

trucks which have weight power ratio of about 18Okg/kw, is considered. The maximuln

grade controls in tenns of design speed is summarised in T'able 4-9A to 4'9F.

(d)

44

7

A Guide on Geometric

TABLE 4-9A: MAXIMUM GRADES FOR Rt. R2. Ul & U2STANDARD ROADS

TABLE 4-9B : MAXIMUM GRADES FOR R3 AND R4 STANDARD R0ADS

TABLE 4.9C : MAXIMUI\{ GRADES FoR u3 AND u4 STANDARD ROADS

TABLE 4.9D z MAXIMUM GRADES FOR R5 STANDARD ROADS

TABLE 4-98 : MAXIMUM GRADES FOR U5 STANDARD ROADS

Type of Terrain/Area Design speed (kph)

30 40 50 60 70 80Flat & Type IRolling & Type IIMountainous & Tvpe III

8

lll6

7

lll5

7

l0l4

lt0t3

1

9

t2

6

8

l0

Type of Terrain Design speed (kph)

50 60 70 80 90 r00FlatRollingMountainous

1

9

r0

7

8

IO

7

8

l0

6

7

9

6

7

9

5

6

8

Area Type Design speed (kph)

40 50 60 70 80Type IType IIType III

9

t2t3

9

t1

I2

9

10

12

8

9

1l

7

8

10

Type of Terrain Design speed (kph)

60 -7n80 90 r00 110

FlatRollingMountainous

5

6

8

5

61

i+

5

7

45

6

a

A-6

aJ

+

5

Area Type of TerrainDesign speed (kph)

s0 60 t0 80 90 r00Type IType IIType III

6q

II

7

8

10

6

7

9

6

7

9

5

6

8

5

6

8

TABLE 4-9F : MAXIMUM GRADES FOR U6 AI{D R6 STAI'{DARD ROADS

Design speed (kType of Terrain/Area

Flat & Type IRolling & Type IIMountainous & TVpe III

The total upgrade for any section of road should not exceed 3000 m unless the grade is

less than 4 Vo.

4.3.2 Minimum Grades

A desirable minimum grade or 0.5 percent should be used. A grade of 0.35 percent may

be allowable where a high type pavement accurately crowned is used' On straight

stretches traversing across wide areas of low lying swamps use of even flatter grades may

be allowabte witn lrior approval. However, the design of the stonn water drainage outlet

should be considered carefully at these location to ensure that flooding of the travelled

lanes is avoided.

Where less than 0.5Volongrtudinal gradient is necessary, the superelevation runofflength

used should be the minimum valul permitted. This will minimise flat area along the

carriageway where the cross falls are less than \Vo. The use of open textule wearing

course at this locations should be considered; this will heip in preventing hydropianing'

4.3.3 Critical Grade Length

The term "critical grade length" indicates the maximum length of a designated upgrade

upon which a loaded truck can operate without an unreasonable reduction in speed' To

establish the design values for ciitical grade lengths, for which gradeability of trucks is

the determining factor, the following assumptions are made:-

(i) The weighr-power rario of a loaded truck is about 180 kglkw.

(ii) The average running speed as related to design speed is used to approximate the

speed of vehicles beginning an uphill climb'

(iii) The common basis for determining the critical grade length is a reduction in

speed of trucks below the averageiunning speed. Studies show that accident

involvement rate increases siglificantly when truck speed reduction exceeds

l5kph. For example accideniinvolvement rate is 2.4 times greater for 25kph

reduction than for a l5kph reduction.

The length of any given grade that will cause the speed of a representative truck

(lS0kglkw) enterin! the grade at 90k1r/h to reduce by various amounts below the

average running rp""O in shown graphically in Figure 4-5. The 25kph speed reduction

curve should be used as the general design guide for determining the critical iength of

srade.

AA

50

300 400 500 600

LEIIGTII OF GRADE (METERS)

FIGT]RE 4-5 : CRITICAL LENGTIIS OF GRADE FOR DESIGNFOR TYFICAL ffiAVY TRUCK OF ltOkslkW'

aDlducnoN i"*l Iiii

+t

A Cuide on Geometric Design of Roads

Where a particular section is made up of a combination of upgrade, the length of critical

grade, measured from tangent point to tangent point, should take into consideration, the

entire section of the combination.

Where the length of critical grade is exceededand especially where grade exceed5Vo,

consideration should be given to providing an added uphill lane, that is, the climbing

lane, for slow moving vehicles, particulariy where the volume is at or near capacity and

the truck volume is hish.

4.3.4 Climbing Lanes for Two Laned Roads

The following conditions and criteria, which reflect economic consideration, should be

satisfied to justify a clirnbing lane:

(i) Upgrade peak traffic flow rate in excess of 2AA vehicies per hour

(ii) Upgrade truck peak flow rate in excess of 20 vehicles per hour

(iii) One of the following conditions exist:

. A 25kph or greater speed reduction is expected for typical heavy truck.

. Level of service E or F exist on the grade

. A reduction of two or more levels of services is experienced approaching the

start of the grade.

Where climbing lanes are provided, the following requirement are to be followed:-

(a) the climbing lanes should begin near the foot of the grade and should be

proceeded by a tapered section of at least 50m iong'

(b) the width of the clirnbing lane should be the same as lhe main carriageway lane

width and in any case should not be less than 3.25m.

(c) the section of the road must be separated by a New Jersey Type Concrete Median

with adequate signing and markings and the opposing lane widened also to 2

lanes to make it a four lane divided carriageway.

(d) the climbing lane should end at least 60m beyond the crest and in particular

should be at a point where the sight distance is sufficient to permit passing with

safety. In addition, a coffesponding taper length as in (a) of l00m should be

provided.

(c) the shoulder on the outer edge of the climbing lane should be as wide as the

shoulder on the normal two laned section. Where conditions dictate otherwise,

a useable shoulder width of 1.25m is acceptable.

48

7

A Guide on Geontetic Design of Roads

4.3.5 Passing Lane Sections on Two-Lane Roads

Wliere a sufficient number and iength of safe passing sectiolt canuot be obtaincd in the

design of horizontal and vertical alignment alone, an occasional section of four lanes

may be introduced to provide more sections and length safe for passing. Such section

are particularly advantageous in rolling terrain, especially where the alignment is

winding or where the vertical profile includes critical lengths of grade. Four lane

sections should be sufficiently long to permit its effective usage.

The sections of four lanes introduced need not be divided. The use of a median, however

is advantageous and should be considered on roads carrying 500 vehicles per hour orlnore.

The transitions between the two lane and four lane pavements should be located where

of change in width is in full view of the driver. Sections of four-lane road, particularly

divided sections should not be longer than 3 km so as to ensure that the driver does not

lose his awareness that the road is basicaliy a two lane facility.

Where four lane sections are not practical, passing one direction lane sections shall be

introduced at regular intervals. The passing lane must be at least 125m long and of fulllane width and preceded by a taper of 50m at the beginning and 100m at the end.

4.3.6 Climbing Lanes on Multilane Roads

Multilane roads more frequently have sufficient capacity to handle their traffic load,

including the normal percentage or slow-moving vehicles without becoming congested.

However where the volume is at or near capacity ( 1700 vehicle per hour per lane) and

the truck volume is high (2107o of total flow) so as to interfere with the normal flow oftraffic then addition of climbine lanes should be considered.

4.3.7 Vertical Curves

Vertical curves are used to effect a gradual change between tangent grades. They should

be simple in application and should result in a design that is safe, comfortable inoperation, pleasing in appearance and adequate for drainage. For simplicity, the

parabolic curve with an equivalent vertical axis centered on the vertical point ofintersection is used.

The rate of change of grade to successive points on the curve is a constant amount for

equal increments of horizontal distance, and equals the algebraic difference between the

intersecting tangent grades divided by the length of curve or A,/I- in percent per meter.

The reciprocal L/A is the horizontal distance in metre required to effect a 1 percent

change in gradient and is a measure of curvature. This quantity (L/A), termed k, is used

in determining the horizontal distance from the beginning of the vertical curve to the

apex or low point of the curve. The k value is also useful in determining the minimumlengths of vertical curves for the various design speeds.

The lengths of vertical curves used should be as long as possible and above the minimumvalues for the design speeds where economically feasibie.

49

A,9uide on Geometic De

(al Crest Vertical Curves

Minimum lengths of crest vertical curves are determined by the sight distancerequirements. The stopping sight distance is the ma.ior controi for the safeoperation at the design speed chosen. Passing sight disiances are not used as irprovides for an uneconomical design. An exception may be at decision areassuch as sight distance to ramp exit gores where iong.r rengths are necessary.

The basis formula for length of a parabolic vertical curve in terms of algebraicdifference in grade and sight distince (using an eye height of l.Orn and objectheight of 0.15m) are as follows:

Where S is less than L, L= AS2404

Where S is greater than L, L= 25 _ 404--'-

Where L = length of vertical curve(m )

S = sight distance (m)

A = algebraic difference in grades (percent)

Table 4-t0A indicates the required K values that areto be used in design for thevarious design speeds.

TABLE 4-r0A: CREST VERTTCAL CURVE (K VALUES)

Sag Vertical Curves

At least four different criteria for establishing lengths of sag verticai curves arerecognised. These are (r) headlight sight distan "",\zlriaer c'omforr, (3) drainagecontrol and (4') a rule of thumb for general use and this criterion is used toestablish the design vaiues for a range of lengths of sag vertical curves. It isagain convenient to express the design control in terms of the K value.

Table 4-108 indicates the minirnum K varues that are fo be used.

Longer curves are desired wherever feasible and should be used, but where Kvalues in excess of 55 are used, special attention to drainage must be exercised.shorter sag verticar curves may bliustified for economic ,Juronr, in cases wherean existing element such as a structure which is not ready for replacementcontrols the vertical profile.

(b)

MinimumK value

50

A Guide on Geometic Design of Raads

Drainage of curbed pavements are especially important on sag vertical curves

where a gradeline of not less than 0.3 percent within 15m of the level point must

be maintained.

TABLE 4-108 : SAG VERTICAL CURVE (K VALUES)

DesignSpeed(km/h)

110 100 90 80 10 60 50 40 30

MinimumK value

62 51 40 a^3L 25 l8 T2 8 4

4.3.8 General Controls for Vertical Alignment

In addition to the specific controls, there are several general controls that should be

considered.

(a) A smooth gradeline with gradual changes should be strived for in preference to

a line with numerous breaks and short lengths of grade. While the maximum

grade and the critical length are controls, the manner in which they are applied

and fitted to the terrain on a continuous line determines the suitability and

appearance of the finished product.

(b) The 'roller coaster' or the 'hidden-dip' type of profile should be avoided. They

are avoided by use of horizontal curves or by more gradual grades.

(c) A broken back gradeline should be avoided, particularly in sags where the full

view of both vertical curves is not pleasing. This effect is very noticeable on

divided roadways with open median sections.

(d) On long grades, it is preferable to place the steepest grades at the bottom and

lighten the grades near the top of the ascent or to break the sustained grade by

short intervals of higher grade instead of a uniformed sustained grade that might

be only slightly below the allowable minimum-

(e) Where intersections at grade occur on sections with moderate to steep grades, itis desirable to reduce the gradient through the intersection.

5l

4"4

Horizontal and vertical alignment should not be designed independent.ly. Theycomplement each other. Excellence in their design and in the desrgn of theircombination increase ufility and safety, encourage uniforrn speecl, and improveappearance, armost arways without acr<iitionar cost.

Proper combination of horizontal alignment. and profire is obtained by engineenng studyand consideration of the following general controls.

(a) Curvature and grades should be in proper balance. Tangent alignment or flatcurvature at the expense ofsteep or long grades, and excessive curvature with flatgrades, are both poor design. A logicaio-esign is a compromise between the two,which offers the most in safety, capacity, ea-se and uniiormity of operation, andpleasing appearance within the pracrical limits of terrain and area traversed.

(b) vertical curvature superimposed upon ho.izontal curvature, or vice versa,generally results in a more pleasing iacility but it should be analysed for effectupon traffic' Successive changes in profile not in combination with horizontalcurvature may result in a series of humps visible to the driver for some distance,ahazardous condition.

(c) Sharp horizontal curvature should not be introduced at or near the top of apronounced crest vertical curve. Their condition is hazardous in that the drivercannot perceive the horizontal change in alignment, especially at night when theheadlight beams go straight ahead into ,pu.!. Thehaiardor tnis ariangement isavoided if the horizontal curve is made longer than the vertical curve. Also,suitable design can be by using design valuesiboue the minimum for the designspeed.

(d) Somewhat allied to the above, sharp hori zontal curvature should not beintroduced at or near the low point of u p.onoun.ed sag verlical curve. Becausethe road ahead is foreshortened any but flat horizontal curvature assumes anundesirable distorted appearance, fufther, vehicular speeds, particularly of trucks,often are high at the bottom of grades and erratic operation may result, especiallyat night.

(e) on 2-lane roads the need for safe passing sections at frequent intervals and foran appreciable percentage ofthe length olthe road often supersedes the generaldesirability for combination of horizontal and vertical alignment. In these cases' it is necessary to work toward long tangent sections to secure sufficient passi'gsight distance in design.

(0 Horizontal curvature and profile should be made as flat as feasible at intersectionswhere sight distance along both roads is important and vehicles may have to slowdown or stop.

52

(e) On divided roads, variation in the width of median and the use of separate

profiles and horizontal alignments should be considered to derive design and

operational advantages of one-way roadways. Where traffic justifies provision

of 4 lanes, a superior design without additional cost generally results from the

concept and logical design basis of one-way roadways.

In residential areas the alignment should be designed to minimise nuisance

factors to the neighbourhood. Generally, a depressed road makes it less visible

and less noisy to adjacent residents. Minor horizontal alignment adjustments can

sometime be made to increase the buffer zone between the road and the

residential areas.

Examples of poor and good practices are illustrated in Figure 4-6 z A to 4-6 : N

below:

(h)

(i)

TANGENT AIIGNMENT

PREFERRED--\

(A) PRONLE WITII TA}IGENT ALIGNMENT

NorE :- AVoID DESIGNING LITTLE LocAt DIps IN AN orrIERwIsE LoNc.UNIFORMGRADE,

PREFERRED

(B) PROFILE WITH CUR.VED ALIGNMENT

NOTE :- sHoRT HUMps IN TIIE GRADE SHOULD BE AVOIDED.

F'IGURE4-6:A&B

LrNE oF srcHrnslTsgEN BoTToMLAND

PREFERRED

PROFILE

(C) DISTANT VIEW SHOWING BUMPS IN PROFILE GRADE LINE

NOTE :- A DISTANT SIDE VIEW OF A LONG GRADE TANGENT WILLREVEAIEVERYBUMP ONIT.

(D) SHORTTAI\IGENT ON A CREST BETWEEN TWOHORIZONTAL CUR\rES

NoTE :- THIS COI.ItsINATION IS DEFICIENT FOR TWO REASONS'

THE TANGENT BEfi[ryEN T}iE CUR\ES IS TOO SHORT, AND TIIE

REVERSE OCCI.'RS ON A CREST.

FIGURE4-6zC&D

ALIGNMENT

55

AlIGMvTENT

PROFILE

(E) SEARP ANGLE APPEARANCE

NOTE:- TT{IS COMBINAfiON PRESENTS A poORA?PEARANCE. T}tEHORZONTAL CLJRVE LOOKS LIKE A SHAR-P ANGLE,

(F") DTSJOTNTED EFFECTNorE :- A DISTOINTED EFFECT occ{tRs WHEN Tr{E BEGINNI}JG oF A HoRIzoNTAL

CTIRVE IS HIDDEN FROM TI{E DRTVER BY A INTERVENING CREST WHILETIIE CONTINUATION OF TI{E CTIRVE IS VISIBLE IN THE DISTANCE BEYONDTHE INTERVENING CREST..

FIGURE4-6:E&F

56

V

SLrt\{MIT

PROFILE

(G) COINCIDTNG CURVES IN HORTZONTAL ANDVERTICAL DIMENSIONS

NOTE :- WHEN HORIZONTAL AND VERTICAL CttRVEs coINcIDE A VERY

SATISFACTORY APPEARANCE RESULTS.

Gr) oPPosrNG cuRvES rN HORTZONTAL ANDVERTICAL DIMENSIONS

NOTE :- WHEN HORIZONTAI AND VERTICAT CURVES OPPOSE' A VERY

SATISFACTORY APPEARANCE RESTILTS.

-MIMMUM CTIRVES FOR TFM

/ DESIGNSPEED

ALIGNMENT

\ ./-\/l-\

L DESIRABLE CURVE FOR APPeeRaNce

-]TI) FLAT C{IRVES APPROPRIATE FOR HORIZONT,AL WITTI. ,

SMALL CENTRAL A}IGLES REGARDLESS OF PROFILE

NOTE:- VERY LONG FLAT CLJRVES, EVEN WHERENOT REQUIRED BY TI{E DESICN

SPEED, AIJO HAVE A PLEASING APPEARANCE WHEN TTIE CE}]TRALANGLE IS VERY SMALL.

FIGURE4-6:G,H&I

ATIGNMENT

57

-]_---\ t\_

t-I

HORTZONTAL AIIGNMENT-*{-

tt

- -

L

-

\ Il-

PROFILE

(o COINCIDING CURVES VERTTCES rN HORTZONTALAND VERTICAL DIMENSIONS

NOTE :- THE CLASSIC CASE OF COORDINATION BETWEEN HORIZONTALAND VERTICAI ALIGNMENT IN WHICH TT{E VERTICES OFHORIZONTAL AND VERTICAL CURVES COINCIDE. CREATINGA zuCH EFFECT OF THREE-DIMENSIONAL S.CLIRVES,COMPOSED OF CO}.IVEX AND CONCAVE IIELD(ES,

l-I

I

I 1-I

j

-

_-

-

HORIZONTAI AI,IGNMENT

'\ -/-\-_-I \

PROFILE

(K) COINCIDING VERTICES WITH SINGLE.PHASE SKIPNOTE :- A LENGITIMATE CASE OF COORDINATION : ONE pHASE IS SKIPPED IN

TI{E HORTZONTAL PLANE, BUT VERTICES STILL COINCIDE. TI{E LONGTANGENT INPI.ANE IS SOF-|ENED BY VERTICAI CT,IRVATURE,

{

I

I

/_----l -..-*--/

--i_I

1 HORLZONTATAUGN},IE{I Itlll__r_

.-----l--"\ \-!--'FROFILE

(L) WEAK COORDINATTON OF EORTZONTAL ANDVERTICAL ALIGNMENTS

NOTE :- A CASE WTIH WEAK COORDINATION WHERE TI{E VERTTCAT ATTGNMENT ISSHIFTED HALF A PTIASE WTTH RESPECT TO HORIZONTAI ALIGNMENT SOT}IE VERTICES COINCIDE WTru POINTS OF IhIFLECTION. TIIE SUPERELEVATIONIN T}IIS CASE OCCURS ON GRADE, WHILE CRESTS AND SAGS TTAVE NORMALCROSS SECTIONS IN TIIE FIRST CASE, SIIPERSLEVATION OCCI]RS ON CRESTSSAGS, WHILE GRADES I{A!E NORh,T,AL CROSS SECTIONS.

FIGURE 4-6 z J,K&L

58

:\o

t$rddF(

-/A\Jl-(-

UtZri fin2 EfiH3 iFr3 EfiH

H 3Fii BsE/ fitr.1A Yi.,r\l v)vHiE XbH? Q?zF Y.6tt)Z xr?rd hFH

Z H;=

3 iHa

i i'a"l"F Z{rltHZ ixFlE FT;HD TEFEF HAfi5l+l rvH*l{AtllE6vz

59

z\o

IvF4tv.-)rlr\JF{r-.-{

mFz-!{azrhv-l.]FI

U-,xo\H7\ > FLI -ZI A <l!, ZAE4 ea-

^>'lr xHts !?<F-4 e -;'ar-l x 42. EEOii Q c.<N fr,92l.l - .^& ''l^2-&A :<pv V r(Jtr i:?Hfa' Z 2 r':i r-(,IJ ENXz eE:o 6 i,E.F-( ,,;

zzA,4F(AvA\,Ql-.1Av

^lvriv

zvk7xe<E>a\aXXqfi<E(JmF>

it

>lI1

\,,1v

Fz€Xfi<x>1stfiFd

t*T>

60

A Cuide on Geometric Design o.f Roads

CHAPTER 5 - CROSS SECTION ELEMENTS

5.1 PAVEMENT

5.f .1 Surface Type

The selection of the pavement type is determined by the volume and composition oftraffic, soil characteristics, weather, availability of materials, the initial cost and the

overall annual maintenance and service life cost.

Pavements may be considered as three general types according to the volume of trafficthey carry - high, intermediate and low. High traffic volume pavements have smoothriding qualities and good non-skid properties in all weather conditions. Intermediatetraffic volume pavements vary from high traffic volume pavements only slightly, are less

costly and with less strength than high traffic volurne pavements. Low traffic volumepavements range from surface treated earth roads and stabilized matertals to loose

surface such as earth and gravel.

The important characteristics of surface type in relation to geometric design are the

ability of a surface to retain the shape and dimensions, the ability to drain, and the effect

on driver's behavior. Table 5-l gives the general selection of the pavement surface

types for the various road standards.

For minor roads of grades exceeding 87o, the surface and shoulder should be sealed to

prevent erosion.

The structural design of flexible pavement should be in accordance to Arahan Teknik(Jalan) - 5/85 "Manual On Pavement Design".

TABLE 5-1 : TYPICAL PAVEMENT SURFACE TYPE

DesignStandard

Description

R6ru6R5ru5R4N4R3ru3RzN2Rlrul

Asphaltic Concrete/ConcreteAsphaltic Concrete/ConcreteDense Bituminous Macadam/Asphaltic Concrete/ConcreteB ituminous Macadam/ConcreteSurface Treatment/Semi sroutGravel/Semisrout

5.1.2 Normal Cross Slope

Cross slopes are an important element in the cross-section design and a reasonably steep

lateral slope is desirable to minimise water ponding on flat sections of uncurbed

pavements due to pavement imperfections or unequal settlements and to control the flowof water adjacent to the curb on curbed pavements. The range of cross slopes for various

pavement types varies from 2.5Vo to 6.0Vo.

6l

A Guide on Geometic Design

5.3 SHOULDERS

The capacity of a llqnwav primarily depends on rhe number of traffic lanes and rheirwidths' The lane width is determin"d uy the size of vehicle, averagedaily traffic volumeof cornmercial vehicies and the requi.emenfs for overtaking and passing.

Marginal strip is a nalrow pavement strip attached to both edges of a cariageway. It ispaved to the same standard as the traffic lanes. For divided roads, the marginal strips areprovided on both sides of the carriageways. The marginal strip is included as part of theshoulder width' Edge line ma.kingire applied to demarcate the through lane and themarginal strip and is to be located within the marginal strip.

Table 5'2 indicates the lane and marginal strip width that are to be used for the variousroad standards.

Note : x denotes the total two_way width

5"3.1 Definition

A shoulder is defined as the portion of the roadway continuous with the traveled way foraccommodation of stopped vehicles, for emergen.f ur. and for laterar support to thepavement.

A typical cross section showing shoulder and verge is as shown in Figure 5.r.

TABLE 5.2 : LANE & MARGINAL STRIP wIDTHs

Design Standard Lane Width (m) Marginal Strip Width (m)

Interchange RamplSingle LaneMulti Lanes

Single Lane

4.503.504.50

Lt 1.50 Rt 0.50Lt 0.50 Rt 0.50Lr 1.50 Rt 0.50

re*ia':r%

az

ou0Lq)

A

-Icq

hc)

aI

-tl-t4

-aq.(

I-.FI+JIq)00rn

Lr\\J-c!I.-gt-t-ltnq)LFI

bo.-r-.H

a)

c)l-!)o-B

II

- --+I{Jl

.61

'H

T-I

I

I r..

-l c)

[)I;>l t

l-rlt)

a

rh

Fbo

'fF

(J

63

:

::


5.3.2 Functions

The main functions of shoulders are :_

(a) space is provided for emergency stoppin g freeo{ the traffic iane.(b) space is provided for the occasirnal motorist who desires to stop for various

reasons.

(c) space is provided to escape pofential accidents or reduce their severity.(d) the sense of openness created by shoulders of adequate width contributes to

driving ease and comfort.

(e) sight distance is improved in cut sections, thereby improving safety.(0 highway capacity is improved and uniform speed is encouraged.(g) lateral clearance is provided for signs and guardrairs.(h) structural support is given to the pavement.

5.3.3 Width of Shoulders

The normal usable shoulder width thatshould be provided along high type facilities is3m' However' in difficult terrain and on low volume roads, usable shoulders of this widthmay not be feasible.

Table 5-3A and 5-38 gives the widths of shoulders for the various road standards inrural and urban areas.

The shoulder widths on structures are defined in Section 5.10. The width of shouldersshould also take into consideration car parks.

TABLE 5-3A : USABLE SHOULDER WIDTH (RURAL)

Usable Shoulder Widrh (m)

Rollin Mountainous

R6R5R4R3R2R1

3.003.003.00)\n2.401.50

3.003.003.002.502.0a1.50

2.5A

2.s02.002.AA

r.50r.50

64


TABLE 5-38 : PAVED SHOULDER WIDTH ruRBAN)

Paved Shoulder Width (m)

Area Type *

I II**. III**

U6U5U4U3U2U1

3.003.003.002.502.001.50

3.003.002.502.001.501.50

2.502.502.041.50

1.50

1.50

* For Area Type definition, see Table 3-28x* For Area Type II & III, U1 to U4, shoulder may be replaced by sidewalk

5.3.4 Type of Shoulders

There are basically two types of shoulders namely paved and unpaved.

Paved shoulders can be either bituminous or concrete surfaced while unpaved shoulders

can be either crushed rock. earth or turf shoulders.

The paved shoulder widths are as shown in Table 5.4. The figures given are in addition

to the width required for parking.

TABLE 5.4 : PAVED SHOULDER WIDTH (RURAL)

DesignStandard

Paved Shoulder Width (m)

R6R5R4R3

Min 2.5Min 2.0

1.5

1.5

The structure and the cross slope of these shoulders are different and they are described

below. .

5.3.5 Shoulder Cross Slope

Ali shoulders should be sloped sufficiently to rapidly drain surface water but not to the

extend that vehicular use would be hazardous. Because the type of shoulder constructionhas a bearing on the cross-slope, the two should be determined jointly.

Bituminous and concrete surface shoulders should be sloped from 2.5 to 6 percent, gravel

or crushed rock shoulders from 4 to 6 percent and turf shoulders 6 percent. Where kerbs

are used on the outside of the shoulders, the minimum cross-slope should not be less than

4 percent to prevent ponding on the roadway.

65

4 9!id" on Geometric De

At superelevated areas, the shoulder cross-slopes should be adjusted to ensure that themaximum ,.roll over,'does not exceed 6 percent.

5.3.6 ShoulderStructure

For shoulders to function effectively, they must be sufficiently stable to supportoccasional vehicle loads, in all kinds of weather without rutting. paved or stabilisedshoulders offer manY advantages in this aspect. The structu.e oi the paved shouldersshould be similar to that of the carriageway for ati design standards. H"*;;;, ;;;;gradients exceed 8vo the shoulders snouti also be close turfed or sealed to preventerosion for R2 and Rl roads.

5.4 KERBS

5.4.1 General Consideration

The type and location of kerbs appreciably affect driver's behaviour and in turn thesafety and usage of a road. Kerbs are uied for drainage control, pavement edgedelineation, aesthetics, delineation of pedestrian walkways and to assist in the orderlydevelopment of the roadside.

Kerbs are needed mostly on roads in urban areas. In rurar areas, the use of kerbs shouldbe avoided as far as possible except in localised areas which has predominant aspects ofan urban condition.

5.4.2 Types of Kerbs

The two general classes of kerbs are barrier kerbs and mountable kerbs and each hasnumerous types and detail design lach may be designed as a separate unit or integrallywith the pavement. They may also be designed wltn I gutter to form a combination kerband gutter sectjon.

Barrier kerbs are relatively high and steep faced and are designed to inhibit or discouragevehicles from leaving the roadway. They should not be used on expressways. Theyshould also not be used where the design speeds """""a 70 kph or in combination withtraffic barriers' They are recommended foi use in builrup areas adjacent to footpathswith considerable pedestrian traffic, where pedestrian traffic is light, a semi-barrier typemay be used.

Mountable kerbs are used to define pavement edges of through carriageways. Forchannelisation islands, medians, outer separators or any other required delineation withinthe roadway, a semi-mountable type may be used.

Figures 5'2A and 5'28 show the various standard types of kerbs that are to be used.

66

t7

FIGURE 5.2A : ROAD KERB DETAILS

TYPE OF K-ERB USF

I,)BA.RRHffiS

|sOF@

B1

t-il

Euiatsts w ucd to inhr'bitvcbicla ftom leving thcrudrry. Tbcycmmadcdf6uc ia boilt-rp rru Edi&@tto fmPatis or o partr withoridablo pctsiu trafficod thc daigl spccd shotdd bclcs rh^n 70 lpL

Typc Bl kab ir garally uscd at

outcr wc of thc supclcvarodscdiou-

Typc 82 tctb shoulda bc ucCfc aorosl ms stimsGcb ud thc aupaclov8tedscd.ioB al i.Mmclo@lleisuf&cmE

EOP@

'N@o?ls

Nomalfy wd fo &l.inariouud drsiDrgc m dlint rs6tioil. lt i6 sitsblc fqall rcads including expnxs*ays.It ir alrc fc uc o bridga whicb

b offsst &on hridgc nililg.

NOTES:-

I. CONCRETE FOR CAST INSMU OR PRECAST CONCRETE KSRB SHALL BE GRADE 30/20.

2. CONCRTTE BEDDING SHALL BE GRADE 15,20.

3. THE FIMSHED KERB SHALL BE TRUE TO LINE, GRADE AND LEVEL TO WITHIN 15M AND

SIIALL PRESENT A SMOOTH A?PEAXANCE FREE FROM KINKS AND DISTORTION.

TYPE OF KERB USE

3.)MOWSUtrS

tgl

"r=L

I

t"l"

pWot@l

Moutrblc Lcrbs t12e Ml udM2 rc dcigncd to discowcwt trEfrc fioE moutBg a

t'affic irlud Roudebou'l s@adis! qc?t for lo.ng qovd-dllmtold volcl6.

TypB M2 kdb6 sc d6igred to

colldt BEf8cc mo{f ud ballow vchicld to @s ovdud to psrk cltr of tbccmirgmy duing magmcY.

1.) GAISIEL I€RJS

Cbrucl kabouldbcwdalonr thc pavod sboulda wbctbc irfad reoffis colidmbtYluee. It is nomrllY wcd oo

d-bshot wbdc dniD hs !o bcphccd dmg tbo pavod sbouldsi--cdiatly i! Asnt of b$iq(GudreilN* JaneY Briq)It ws dairncd to minimiz thcavce cffi(' of thc cbruclon tbc stairg md vcbiclcsboulds bc sblo to drivc ovathis chancl nfcly.

61

20 i00 50 100 (mi!.)

--mnm$

SECTION A-A

l00m CONCRETEFOI'NDATION

FTGURE 5.28: ROAD KERB DETAILS

TE PIPE

WITH RECTA IEULAR OPENING

()2

ya

FRONTVIEW OF KERB

1300r

68

.7

A Guide on Geomelric Design d Roads

The width of kerbs are considered as cross section elements entirely outside the trafficlane width. However, for drainage kerbs, the gutter section may be considered as pan ofthe marginal strip. Where roadways do not have any marginal strip, kerbs should be

offsetted by a minimum of 0.25 m.

5.4.3 Channel Kerbs

Channel kerbs should be considered for roads built on hieh embankment and for roads

with wide roadway.

SIDEWALKS

Sidewalks are accepted as integral parts of urban roads and should be provided except

on Urban Expressways or Major Arterials where the presence of pedestrians are minimal.

However, the need for sidewalks in many rural areas is great because of the high speed

and general lack of adequate lighting and due consideration must be given for itespecially at points of community development such as schools, local business and

industrial plants that results in high pedestrian concentrations. While there are no

numerical warrants, the justification for a sidewalk depends on the vehicle-pedestrian

hazard which is governed by the volumes of pedestrian and vehicular traffic, theirrelative timing and the speed of the vehicular traffic.

In urban areas, sidewalks can be placed adjacent to the kerbs and raised above the

pavement. In the absence of kerbs, a strip of a minimum width of l.0m must be provided

between the sidewaik and the travelled way.

In rural areas, sidewalks must be placed well away from the travelled way and separated

from the shoulder by at least 1.0m.

A desirable width of 2.0m is to be provided for all sidewalks. Where there are restrictions

on right of way, a minimum of clear width of 1.5m can be considered. When provided,

sidewalks must have all weather surfaces. There must be no obstructions on sidewalks.

TRAFFIC BARRIERS

Traffic barriers are used to minimise the severity of potential accident involving vehicles

leaving the traveled way. Because bariers are ahazard in themselves, emphasis should

be on minimising the number of such installations. Arahan Teknik (Jalan) l/85 "Manual

On Design Guidelines of Longitudinal Traffic Barrier" (May, 1984) should be used for

the design of longitudinal traffic bariers.

MEDIANS

5.7.1 General

A median is a highly desirable element on all roads canying four or more lanes and

should be provided wherever possible. The principal functions of a median are to provide

the desired freedom from the interference of opposing traffic, to provide a recovery area

for out-of-control vehicles, to provide for speed change and storage of right-tunringvehicles and to orovide for future lanes.

5.6

5./

69

A Guide on Geometric

For maximum efficiency, a median should be highly visible both night and day and indefinite contrast to the through traffic lanes.

5.7.2 Median Width

Medians may be depressed, raised or flush with the pavement surface. They should beas wide as feasible but of a dimension in balanceo wltn other components of the cross-section. The general range of median width varies from a minimum of l.5m in a AreaType III urban situation to a desirable width of l8 m on a rural expressway. on widemedians, it is essential to have a depressed centre or swale to provide for drainage.

Table 5-5A and 5-58 gives the minimum and desirable widrhs and types of medians rharare to be applied to the various road standards. The median widths u,

""prrrr.d are the

dimensions between the through lane edges and includes the right shouiders if any.

5.8.1 General

Service roads are generally found in urban areas and they can have numerous functions,depending on the type ofroad they serve and the character of the sunounding area. Theymay be used to control access or function as a street facility serving adjourning property.

They segregate local traffic from the higher speed through traffic and intercept drivewaysof residences and commercial establishments along the road. Service roads also not onlyprovide more favourable access for commercial ind residential development than thefaster moving afterials but also helps to preserve the safety and capacity of the latter.

TABLE 5-5A : MEDIAN WIDTH (RURAL)

Median Width (mTerrain

Rollin MountainousMinimum Minimum Desirable Minimum

TABLE 5.58 : MEDIAN WIDTH ruRBAN)

Median Width (m)

Minimum Minimum

70

'17

A Guide on Geometic Design of Roads

5.8.2 Design Requirements

From an operational and safety standpoint, one way service roads are much preferred totwo-way and should be considered. One-way operation inconveniences local traffic tosome degree, but the advantages in reduction in Vehicular and pedestrian conflicts atintersecting streets often fully compensate for this inconvenience.

Two-way service roads may be considered for partially developed urban areas where theadjoining road system is so irregular and disconnected that one-way operation wouldintroduce considerable added travel distance and cause undue inconvenience. Two-wayservice roads may also be necessary for suburban or rural areas where points of accessto the through facility are infrequent; where the service roads are widely spaced or wherethere is no parallel street within reasonable distance of the service roads in urban areasthat are developed or likely to be developed.

The design of a service road is affected by the type of service it is intended to provide.When provided, they should always cater for at least one side on-street parking. Theyshould be at least I .25 m wide for one-way operation and9.25 m for two-way operation.Figure 5.3 gives the recommended layout for a two-way operation service road frontingan urban arterial where the distance between junctions is greater than 0.5 km. Theminimum reserve width for a service road is 12 m.

7l

AH

Av&tr1U-{t4.-F]0

FIAv

Ft(f)

rnr4tY.-t>)rhv-(-.-l

I

I

Itl

v

A Guide on Geometric Desigrr of Roads

5.9 U.TURN

5.9.1 General

U-turns are categorised into two (2) types:

i) Dedicated U-turn - These U-turns are grade separated from the through traffic.This form of U-tum should be considered for high speed and high volumehighway as the diverging and merging movements are on the slow lanes.

ii) Median Opening U-turn.

5.9.2 Location of U-Turns

U-turns may be required in the following circumstances:

a) Beyond intersections to accommodate minor turning movements not otherwiseprovided in the intersection or interchange area.

b) Just ahead of an intersection to accommodate U-turn movements that wouldinterfere with through and other turning movements at the intersection. Wherea fairly wide median on the approach roadway has few openings, U-turning is

necessary to reach roadside areas. Advance separate openings for U-turn outsidethe intersection proper will reduce interference.

c) In conjunction with minor crossroads where traffic is not permitted to cross the

major road but instead is required to turn left, enter the through traffic stream,

weave to the right, U-turn, then retum. On high-speed or high-volume roads, the

difficulty and long lengths required for weaving with safety usually make this

design pattern undesirable unless the volumes intercepted are light and the

median is of adequate width. This condition may occur where a crossroad withhigh volume traffic, a shopping area, or other traffic generator that requires a

median opening nearby.

d) Locations occurring where regularly spaced openings facilitate maintenanceoperations, policing, repair service of stalled vehicles, or other highway-relatedactivities. Openings for this purpose may be needed on controlled-access roads

and on divided roads through undeveloped areas.

e) Locations occuming on roads without control of access where median openings

at optimum spacing are provided to serve existing frontage developments and at

the sanre time minimize pressure for future ntedian openings.

The locations of U-turns are very important and traffic safety should be given dueconsideration. As a general guide, Table 5.6 can be used to detennine the desirabledistances between U-turns.

13

A Guide on Geometric Design

TABLE 5.6 : DESIRABLE DISTANCE BETWEEN U.TURNS

5.9.3 DesignConsideration

u-turning vehicles interfere with through traffic by encroaching on part or all of thethrough traffic lanes. They are n11de uilo* speeds and the required speed change isnormally mad^e 91

the through traffic Ianes with weaving to and riom ttre outer lanes. Assuch, U-turn facilities are potentialhazard areas. Careful consideration should be madeto design and locate the u-turn that are safe for ail the road users.

For direct u-turns, the width of the highway, including the median should be sufficientto permit the turn to be made without encroachment beyond the outer edges of thepavements' Figure 5'4 gives the minimum width of the median required for the varioustypes of maneuvers for direct U_turns.

The U-turn should be designed such that the through traffic approaching the U-turn aretravelling at much lower than the highway desigipeed. Traffic signage and calmingdevices, etc. should be considered.

Distance BetweenU-Turns

Design j Distance BetweenStandard I U-Turns

R6R5R4

No U-turns allowed3km2km

U6U5U4U3

No U-turns allowed2kmlkmlkm

74

tr

YF)z)<!lFtsFi IIt

=>,r.Z6gltcnF.X

F6p

2,

=

lr|I

t-.,1

B

c'l t.-t'.- +

v)\ t--

a-m

prtl

z

fr.

rTl

t*

tr-''1

,l:l

\

zzJ.l/,9 e77zz

EZa

&9 *,rI)FFzqz7

zx{EIpCzxa6

u)zfrt)tr

I

-F(JFEi

*FIH

ilv-t7r4vl-(cnf;rliAFl

E,-,-izFI

E!tr

IrnF'tY.F(

l-rhvHf-.FI

75


5.10

5.10.1 Width of Shoulders

The width of the usable shoulders should follow that as indicated in Table 5-3A and5'38. The width of the shoulder of bridges and structures should be the same as that ofthe carriageway.

Figures 5.5 show the typical bridge cross section.

5.10.2 Required Clearance

The vertical height clearance of all structures above the roadway shall be aminimum of 5.3 meters over the entire width of traffic lanes, auxiliary Ianes andshoulders. It is recommended that an additional 0.1 meter be allowed for futurepavement resurfacing. Whenever resurfacing will reduce the clearance to lessthan 5.3 meters, milling will be required to maintain the minimum clearance.

For ciearance requirements over railways and waterways, reference should bemade to the relevant authorities.

Figure 5.6 indicates the clearance requirements for undemasses of various crosssections.

(a)

(b)

(cJ

5.11 BUS LAYBYES

Bus laybyes serve to remove the bus from the through traffic ianes. Its location anddesign should therefore provide ready access in the safest and most efficrent mannerpossible. The basic requirement is that the deceleration, standing and acceleration of thebuses be effected on pavement areas clear of and separated fromihe through traffic lanes.

The locations of bus laybyes are impoftant so as not to impede the normal flow of traffic.In this respect, bus laybyes must not be located on any interchange ramps or srmctures,slip roads or within 60 m of any junction or intersection. The distance between laybyestoo should not be less than 150 m. Liaison will need to be made also with the relevantbus companies and the respective Local Authority.

For school areas, provision of bus laybyes and parkings areas should be specificallystudied so as to ensure the unirnpederj flow of triffic.

Figure 5.7 shows the typical layout and dimensions of bus laybyes that are to be usedin both rural and urban areas. If possible, a dividing area between the outer edge of theroadway shoulder and the edge of the bus laybye lane should be provided. This dividingarea should be as wide as possible but not less than 0.6 m.

The pavement areas of the laybyes should be of concrete or other material fbr contrastin coiour and texture with the through traffic Ianes to discourage through traffic fromencroaching on or entering the bus stop.

/o

(t)zFUrT'l

0a(t)

Otrl ,rx3d3,.tnd.ros=a>o?zn(nF]

fri

tr(t).l^s> t\ c.l

-qa

acfl (n ct c.t

a?l(9-<U

?U

r- r|\o \o \o

ry&ft<nzx<HF

(n

rl

*<t

ca;)

c\lDct

I

17

FIGURE 5.6 : CLEARANCES

LEFT CLEARANCES

AT UNDERPASS

RIGHT CLEARANCES

3.0 m (Desirable)1.5 m (Minimum)

TRAfFIC LANES

CENTRE PIER OR ABU"TMENT-A-

WITH SHOTILDER ONLY-D-

r om(MrNrMUrr{) ;ff,lHtrff]

SIDEWALK (2.0 m)

BARRIER KERB-B-

WITH SIDEWALK-E-

2.0 m QDesirable)1.25 m (Minimnm)

5.3 m

WITH AIIXTLIARY LANE-c-

WITH AIIXILIARY LANE-F-

2.0 m (Desirable)1.25 n (Minimum)

5.3 m

'78

g7(t)zE

r! nl N

o Noal FI

6x-HYlzx<HF

t p c{

aFd

tr

F]aPtrFrAvEl,-\J

:\latrl&FlgF(tr

c{r

:

I

-T

l

i

:

i

I

AF

zv)z

m rl aio

s t\, cll 6|

Qex!-a zx<tsF

&i(?& x.

.{& *

A Guide on Geometric Design

6.1

CHAPTER 6 . OTHER ELEMENTS AFFECTING GEOMETRIC DESIGN

ROAD SAFETY

Road safety has been a much neglected area in the design of roads, With an increasingnumber of accidents each year, attention to road safety should be emphasised, While theroad element is oniy one of the three groups of influences causing accidents, it isnonetheless the responsibility of the designer to provide as safe a road environment aspossible,

In this aspect, the road design should be one with uniformly high standards appliedconsistently over a section. It should avoid discontinuities such as abrupt major changesin design speeds, transitions in roadway cross-section, the introduction of a short-radiuscurve in a series of longer radius curves, a change from full to partial control of access,constrictions in roadway width by narrow bridges or other structures, intersectionswithout adequate sight distances, or other failures to maintain consistency in the roadwaydesign. The highway should offer no surprises to the driver, in terms of either geometricsor traffic controls.

The tendency to base- road designs upon minimum standards rather than to adopt anoptimum design is unfortunate and must be avoided. A more liberal and optimum designmust always be considered, and although it would cost a little more in terms of capiLlcost of the project, it would increase the road's level of safety substantially.

All too often' minimum design standards attempt to rely, on the use of warning signs orother added roadside appurtenances for the safe operat;on that could have been built inby the use of higher design standards. Often tle safety deficiencies generated byminimum design are impossible to correct by any known tiaffic device or ippurtenance.A warning sign is a poor substitute for adequate geometric design.

]n the light to improve road safety, Road Safety Auditing (RSA) has been introduced inMalaysia since 1994-_It is a formal process to identify deficiencies in road design atdifferent stages as welr as to identify hazardous features on existing roads for erimrnationso as to make the road safer for all road users.

RSA is carried out in five stages. The feasibility and planning stage (Stage r),preliminary design stage (stage2), detailed design itage (stage 3), pre-opening stage(Stage 4) and operationaVaudit of existing roads lStage S;.

Rgference on RSA should be made to the "Guidelines For The Safety Audit Of RoadsIn Malaysia" published by the Roads Branch, pubiic works Department Malaysia.

D&AINAGE

Road drainage facilities provide for carrying water across the right of way and forremoval of storm water from the road itself. These facilities include bridges, culverts,channels, gutters and various types of drains. Drainage design considerations are anintegral part of geometric design and flood plain encriachments fiequently affect thehighway alignmenr and profile.

j

6.2

80

6.4


6.3

The cost of drainage is neither incidental nor minor on most roads. Careful attention to

requirements for adequate drainage and protection of the highway from floods in allphase of location and design will prove to be effective in reducing costs in both

construction ant maintenance.

Reference should be made to the relevant JKR manual on this subiect.

LIGHTING

Lighting may improve the safety of a road and the ease and comfort of on operationthereon. Lighting of rural highways may be desirable but the need is much less than on

roads in urban areas. They are seldom justified except on critical portions such as

interchanges, intersections, railroad grade crossings, narrow or long bridges, tunnels and

areas where roadside interference is a factor.

Where lighting is being considered for future installation, considerable savings can be

effected through design and installation of necessary conduits under the pavements and

kerbs as part of the initial construction and should be considered.

Reference should be made to the relevant JKR manual on this subiect.

UTILITIES

All road improvements, whether upgraded within the existing right of way or entirely on

new right of way, generally involves the shifting of utility facilities. Although utilitiesgenerally have little effect on the geometric design of the road, full consideration should

be given to measures necessary to preserve and protect the integrity and visual qualityof the road, its maintenance efficiency and the safety of traffic.

Utilities relocation shouid form part of design and the designer should liaise closely withthe relevant service authorities in determining the existing utilities and their proposed

relocation.

SIGNING AND MARKINGS

Signing and marking are directly related to the design of the road and are features oftraffic control and operation that the engineer must consider in the geometric layout ofsuchfacility. The signing and marking should be designed concurrently with the

geometrics as an integral part, and this will reduce significantly the possibility of future

operational problems. The signing and marking should follow the standards that have

been established. Reference should be made to Arahan Teknik (Jalan) 2A,2F.,2C and

2D on the design, usage and application of signs and markings.

TRAFFIC SIGNALS

Traffic control signals are devices that control vehicular and pedestrian traffic by

assigning the right of way to various movements for certain pretimed or traffic actuated

intervals of time. They are one of the key elements in the function of many urban roads

and should be integrated with the geometric design so as to achieve optimum operational

efficiency.

6.s

6.6

81

ENVIRONMENTAL IMPACTS6.7

Erosion prevention is one of the major factors in design, construction anclof highway. It should be considered early in the location and design stages.of erosion control can be incorporated into geometric design, particularlysection elements.

matntenanceSome degreein the cross-

Landscape development should be in keeping with the character of the road and itsenvironment. The general are of improvement include the followins:

(a) preservation of existing vegetation(b) transplanting of existing vegetation where feasible(c) planting of new vegetation(d) selective clearing and thinning(e) regeneration of natural plant slecies and material.

Landscaping of urban roads assume an additional importance in mitigating the manynuisances associated with urban traffic. Reference stroulO be made to the relevant JKRmanual on this subject

The highway can and should be located and designed to complement its environment andserve as a catalyst to environmental improvement. The area surrounding a proposedhighway is an interrelated system of natural, manmade and sociologic variables. Changesin one variable within this system cannot be made without some effect on other variable.Some of these consequences may be negligible, but others may have strong and lastingimpact on the environment, including the sustenance and quality of human lif.. B".uur"highway location and design decisions have an effect on udju""n t areadevelopment, itis important that environmental variables be given full consideration. Environmentalimpacts include social, economic and physical impacts. In geometric design, onlyphysical impact- are aasessedl while the social and economic impacts would have beentaken care of during the planning stage.

82

1W!1EF@@jfwF1,[email protected] --


REFERENCES

l. ARAHAN TEKNIK JALAN 8/86: A Guide on Geometric Design of Roads, 1986

2. ISMAIL, MOHD. A: Thesis on Review of Highway Geometry Design Standards inMalaysia, 1996

3. AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATIONOFFICIALS (AASHTO): A Policy on Design of Urban Highways And Arterial Streets,

r913

4. THE INSTITUTION OF HIGHWAYS AND TRANSPORTATION WITHDEPARTMENT OF TRANSPORT: Roads and Traffic in Urban Areas, 1987

5. TRANSPORT ROAD RESEARCH LABORATORY AND OVERSEAS

DEVELOPMENT ASSISTANCE. UNITED KINGDOM : TowaTds SafeT ROAdS iN

Developing Country, 199 I

6. JABATAN PERANGKAAN MALAYSIA: Banci Penduduk Malaysia, 1991

7. JABATAN PERANCANG BANDAR DAN DESA: Manual Piawaian Perancangan,

JPBD (IP) S.273 FN/HHffeb. 1998

8. AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATIONOFFICIALS (AASHTO): A Policy on Design of Highways And Streets, 1994

9. TRANSPORTATION AND RESEARCH BOARD: Highway Capacity Manual, Special

Report 209,1985

10. HIGFIWAY PLANNING UNIT, MINISTRY OF WORKS MALAYSIA: Trip Generation

Manual 1997.

83

*n5+f.!ry,'qw-:w


ACKNOWLEDGEMENTS

PUBLIC WORKS DEPARTMENT, MALAYSIA

Dato'Ir. Hj. Zainibin Omar

STANDING COMMITTEE ON TECHNOLOGY AND ROAD MANAGEMENT

Dato' Ir. Chew Swee Hock (Chairman)

TECHNICAL COMMITTEE ON GEOMETRICS ffC3)

Ir. Han Joke Kwang (Chairman)Ir. Koid Teng Hye (Secrerary)Ir. Aznam Abdul Rahim (WG Leader)Ir. Tai Meu Choi (WG Leader)Ir. Sam El-Ashwawi (WG Leader)

84

REAM Guidelines On Geometric Design of Roads

Documents

Transcript of REAM Guidelines On Geometric Design of Roads