The design of road junctions is one of the most important tools of traffic management, which includes the management of demand for movement. The use of junction design in demand management can be usefully informed by analysis of the effect of changing the flow of traffic making each particular movement through a junction upon the conditions encountered by this traffic and by the traffic making each of the other possible movements through the same junction. Existing analysis of this kind is brought together here and extended to cover vehicular traffic at signal controlled junctions, roundabouts and priority junctions in a unified way. The starting point is the identification of traffic movements and how they combine to form separately queuing streams. The sensitivity of the capacity of each stream to the arrival rate in each movement is then analysed. For signal-controlled junctions where signal timings are optimised these sensitivities can be derived readily from the results of the optimisation. For roundabouts and priority junctions, simultaneous linear equations for the sensitivities are constructed by identifying heuristically in which streams the arrival rate exceeds the prevailing capacity. Using these sensitivities, the effects on conditions encountered by traffic in each stream follow from standard approximate expressions for time-dependent amounts of traffic queuing and delay incurred. (A) Reprinted with permission from Elsevier. For the covering abstract see ITRD E134766.
Abstract