The purpose of road junctions is to transfer road users from one traffic stream to another safely and efficiently. Road junctions can be divided into five main groups: (1) Uncontrolled junctions; (2) Priority intersections; (3) Roundabouts; (4) Signal-controlled junctions; and (5) Grade-separated junctions. Some junctions may combine elements of more than one group, e.g., a signalised roundabout with a flyover. This chapter does not deal with the design of traffic signals. A road junction needs to be designed for safe and efficient use by all road users. The designer's task is a matter of balancing these requirements with the needs and concerns of society at large, which can include environmental and political demands (AustRoads, 1988, 1993, 1995, 1999; Department of Transport (U.K.), 1994-2000). Care needs to be taken to ensure that the junction strikes the right balance between all these (often conflicting) requirements.
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