Construction of Passing Points

7/31/2019 Construction of Passing Points

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International Focus Group on Rural Road Engineering

Information Note

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Construction of passing points

Category : Technical Information/Road safety/

PROBLEM

Constraints of geometry or traffic prevents traffic passing safely and easily; single

lane road with no shoulders or weak shoulder materials

SOLUTION

Design and Construction of Passing Places

GENERAL DESCRIPTION

Road widths should be minimised so as to reduce the costs of construction andmaintenance whilst being sufficient to carry the traffic volume and type safely. Other

factors, such as terrain and demands of non-motorised traffic (NMT) may also

determine the optimal road width. Access roads, carrying low traffic volumes, are

likely to be single lane (2.5 3.0m wide). In these circumstances, the frequency of

vehicles meeting is low and over-taking or passing movements should be expected to

be undertaken at low speed.

Provision of a 3.0 metre carriageway with 1.5m shoulders will allow a total road

width of 6.0m, sufficient for two trucks to pass with reasonable clearance at low

speed. Shoulders used by NMT and pedestrians reduces potential conflict to an

acceptably low level.

Road widening or passing points can be considered where:

the shoulder material is weak or the side slopes are steep, and traffic finds

difficulty passing

traffic volumes (both motorised and non-motorised) increase and instances ofconflict compromise safety
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type of traffic (wide commercial vehicles causing passing constraints) orconstraints of geometric design prevents safe and easy passing manoeuvres .

driver education and enforcement is such that operation of mixed single lane-contra-carriageway flows and passing points pose unacceptable safety

problems.

FEATURES

A passing point is a short length of widened road with a taper at each end. It appears

similar to an elongated bus stop or a lay-by. The structure and surface of the passing

point is the same as the main carriageway. The most important feature of passingpoints is the frequency at which they are constructed along the road. The frequency

depends upon the volume of traffic and the road safety environment.

Selection of Passing Points

Single lane road with passing

points

Two lane road

Criteria Suitability

Funding Funds are constrained Funds are not constrained

Traffic volume Traffic volume is below 20vehicles per day

Traffic volume is above 20vehicles per day

Traffic growth Expected traffic growth is less

than 10% per year

Expected traffic growth is

more than 10% per year

Vehicle types Predominantly small vehicles Considerable number ofwide vehicles

Maintenance

practice

Current maintenance practicesuits narrow roads

Current maintenancepractice does not suit narrow

roads

DESIGN ASPECTS

A clear distinction should be drawn between passing points and lay-bys. Lay-bys are

provided for specific purposes, such as parking or bus stops.

Passing points are simple to design in structural terms, following that of the main

carriageway. The greater difficulty is to determine the spacing, location and size of

the passing points. Determination of the optimum passing point spacing is dependent


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on a number of interacting factors (see list) and as such no rigid rules are applicablefor basic access roads.

Spacing and location depend upon the following factors.

Meeting sight distances

Traffic volume and mix

Acceptable reversing distance for vehicles

Terrain

Strength of surrounding ground

Meeting Sight Distances: The spacing and location of passing points is largely

dependent on the meeting sight distances. Ideally, at least one passing point is placed

within each sight distance. Meeting sight distance refers to the length of road wheredrivers in vehicles travelling towards each other begin to see each other. The

maximum spacing and location of passing points is dependent upon sight distances.

Locate passing points such that if one stands at one passing point, the next is visible in

each direction. In hilly terrain the spacing of passing points will need to be moreflexible and responsive to both sight distance and the constraints of the surrounding

landscape. As a general rule the optimal spacing should be equal to the sight distance,up to a maximum of 500 metres. An alternate approach to locate passing places at

regular intervals (say every 500m).

Traffic volume and mix: As traffic volumes increases or the type of traffic

changes (timber trucks, mining vehicles, buses, slow moving motorised/non-motorised), the number of passing points will increase. In such instances road

widening is more likely to become the optimal solution. Drivers of heavy or wide

vehicles may be unwilling to reverse long distances. Where trucks are travelling inboth directions, it may be necessary to reduce the passing point spacing.

Sizing of passing point After determining the spacing and location of passing

points, the length and width should be set. The length is primarily dependent on the

traffic volume. If the traffic volume is high, the passing point should be long enough

to accommodate several vehicles waiting for oncoming traffic to pass.

General Guide for length (including tapers) of passing points

Traffic volume (vehicles

per day)

Required length of

passing point

< 20 25m

20 30 50m

>30 75m

The width of a passing point should be such to allow two trucks to pass, i.e. minimumwidth of 5.0 metres total width. Vehicles should be expected to stop or slow to very

low speed.


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CONSTRUCTION ASPECTS

The construction of passing points is similar to that of the main carriageway.

Side drains The side drain next to the passing point should be protected fromerosion damage where water changes direction.

Signage

Signs indicating the presence and frequency passing points should be provided. Signs

should be highly visible through dust, mist and at night.

Passing points can be delineated using earth or concrete filled oil drums that havebeen pained white. Oil drums can be placed close (10-15m) to the entry and exit of

the passing place.

Construction of Passing Points

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