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T.P.D.M.V.2.4
4.2 Junction Design - General
4.2.1 Introduction
4.2.1,1 Junction design is the most important factor affecting safety and efficiency of movement
within a road network. This chapter contains information to assist the designer in choosing
the most appropriate type of junction control and designing the optimum layout for that
junction type.
4.2.2 Junction Types
4.2.2.1 Junctions can be divided into four main types, viz Priority Junctions, Signal Controlled
Junctions, Roundabouts and Grade Separated Intersections.
4.2.2.2 Priority Junctions operate on the basis that traffic on the major road has continual priority
over the traffic on the minor road. Minor road traffic is controlled by "stop" and "give way"
signs and associated carriageway markings. The onus is entirely on the minor road traffic to
decide when it is safe to enter the major road. Section 4.3 of this chapter covers Priority
Junctions.
4.2.2.3 Signal Controlled Junctions operate on a time sharing basis. Traffic streams are allowed to
enter the junction for a period of time, indicated by an illuminated signal, and during which
period conflicting traffic streams are halted. Volume 4 of this Manual deals
comprehensively with Traffic Signals. Brief mention is made in Section 4.4 of this chapter
purely for reference purposes.
4.2.2 A Roundabouts could be considered as a form of channelized Priority Junction. Vehicles enter
a one way carriageway and move in a clockwise direction around a central island. Entering
vehicles give priority to those vehicles already circulating across their entry. Section 4.5
deals with Roundabouts.
4.2.2.5 Grade Separated Intersections are junctions where some or all of the intersecting roads pass
each other at different levels. Some or all of the turning movements are catered for by
ramps connecting the two levels. Types of interchange and design considerations are
covered in Section 4.6.
4.2.2.6 Junctions may be formed by a combination of two or more of the four basic types described
above. For example grade separation of two major roads with connecting ramps terminating
at roundabouts is quite common.