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A wide range of signal switching policies may be adopted for control of traffic flow between a pair of intersections. One of the most import,ant traffic situations is that in which rush-hour commuter traffic travels towards or away from a city center along radial roads. Under these circumstances opposing and tangential flow may be light. Earlier papers have shown that a modified form of the Dunne-Potts switching policy might be applied to pairs of intersections carrying commuter flow. Efficient and flexible operation of the system under a wide variety of flow conditions, and with the minimum of computer surveillance, was demonstrated. The present paper reports the results of further simulation experiments and discussed tentative solutions of some of the practical problems associated with the proposed scheme. [ABSTRACT FROM AUTHOR]

Hillier has described a method of selecting offsets to minimize delay in certain networks controlled by fixed-time signals. In this paper an attempt is made to extend the method by relaxing somewhat the restriction on the form of the network. The problem is expressed in terms of the theory of graphs, and an iterative process is developed for finding a set of offsets that minimizes delay over the whole network. At each stage, the part of the network already covered is extended by adding one or more links, and for the method to be viable these links must be chosen so that a certain set of intersections remains small. A method of selection of links that minimizes this set of intersections at each stage is developed. The selection of links and calculation of offsets have been programmed in Fortran. Having found one delay-minimizing set of offsets, some others that give the same total delay can be found if they exist. [ABSTRACT FROM AUTHOR]