TRANSPORT PLANNING AND TRAFFIC ENGINEERING 4TH EDITION. CHAPTER 20: INTERSECTION DESIGN AND CAPACITY

The two key considerations of intersection design are to maximise road safety and ensure that the available capacity adequately meets operational traffic-flow needs. Intersections can be classified by geometry into T and Y junctions, crossroads, multiway junctions, or staggered junctions, and also by control mode into uncontrolled, priority controlled (stop, give way), space-sharing (roundabouts), time-sharing (traffic signals), or grade-separated (including interchanges). The process of designing at-grade intersections includes collection of traffic and site data, preparation of preliminary designs by iteration, layout selection, and preparation of the final design using appropriate design standards. There are 13 basic design principles, for example: minimise conflict between traffic streams, favour high priority traffic movements, discourage undesirable traffic movements, and provide refuges for vulnerable road users. There are at least seven other relevant design considerations. The chapter also gives some details of the design and characteristics of: (1) priority intersections; (2) roundabouts; (3) traffic-signal-controlled intersections; and (4) intersections with grade separations. For the covering abstract, see IRRD 892228.