If the generalised cost to a vehicle of travelling along each link in a road network is a suitable known increasing function of the traffic flow on that link, and the number of journeys made per unit time between each point of entry to the network and each point of exit from it is a suitable known decreasing function of the generalised cost to a vehicle of travelling between the two points concerned, or is in accordance with a suitable gravity model, then the techniques of trip distribution and traffic assignment, together with suitable assumptions about drivers' choice of route, enable estimates to be made of the number of journeys between each entry point and each exit point, and the flow of traffic on each link. When all or part of the network is subject to traffic control, the relationships between travel cost and traffic flow on some or all of the links in the network depend on the control parameters, and these can therefore be used to influence the number of journeys made through the network and the routes taken. In this paper, a theoretical framework is developed for such use of traffic control when the method of control is linked traffic signals. The estimated numbers of journeys and traffic flows given by trip distribution and traffic assignment are treated as functions of the traffic control parameters so that these parameters can be chosen so as to improve the traffic pattern with respect to a suitable criterion. An examination is made of the possibility of using trip distribution, traffic assignment and traffic signal calculation techniques to investigate what the results of choosing traffic signal settings in this way might be. A numerical example is given for a simple situation in which a beneficial result could be achieved. (a) for the covering abstract of the symposium please see irrd abstract no. 224453.
Samenvatting