CONTROL AND ROUTEING OF TRAFFIC IN A ROAD NETWORK

A method is described by which traffic management measures, which may affect the routeing of traffic over a large area, may be examined (and, furthermore, suggested) by means of appropriate combinations of system-optimisation and user-optimisation in assignment for given fixed demands between origins and destinations, and co-ordinated signal optimisation in control for given stage ordering and safety requirements. The method takes into account the effects of platooned traffic between co-ordinated signals, turning traffic, weaving traffic on high-speed roads, priority junctions and bus priorities. Time dependence of origin-destination demands, and network overloads, are then discussed. It is shown how the method can be extended in order that such overloads can, to a certain extent, be avoided by the derivation of appropriate cordon control policies. It is further shown how the method can be readily extended to deal with the case of elastic demands between origins and destinations. The method has been incorporated, over the last four years, into a computer program which is currently being used to examine the effects of alternative control strategies in a road network represented by 3500 links, which contains 174 signal-controlled junctions and 34 kilometres of high-speed road. (Author/TRRL)