junctions are where accidents and congestion are most likely to occur. Even the design of a simple crossroads is quite complex. Vehicles enter from four directions and leave the junction at any of the other three directions, by turning left, right or going straight ahead. In doing so they slow to change direction, cross the path of other vehicles or merge into another lane of vehicles. Each of these manoeuvres is potentially a place where there is a conflict between one vehicle and another. At a crossroads there are thirty-two conflict points.
In addition to the vehicle-vehicle conflict points, we can add the routes that pedestrians and cyclists may wish to take across the junction. In order to reduce the number of conflict points, there may be roundabouts, traffic lights or one-way roads, or a combination of all.