THE USE OF THE TRRL TRANSYT METHOD

The paper describes trials, applications and extensions to the method of calculating the best way of co-ordinating fixed-time traffic signals. Transyt consists of two parts: (1) a deterministic traffic model which is used to predict queuing behaviour; and (2) an optimising strategy which automatically searches for the best settings of the signals. Trials were carried out in London and Glasgow and independent evaluations have been made in several countries. In no case so far reported has any other control strategy been found to give an overall advantage over transyt. The computer program has been extended and it is now possible to model and minimise passenger, as opposed to vehicle, travel time. Used in this way, transyt finds fixed-time signal plans which give a measure of priority to buses (bus transyt). A stream of traffic which queues at A common stopline can be separated into up to 5 classes and the movement of these classes can be traced through A network. This facility is used in bus transyt and also to estimate the journey speed of vehicles which follow A particular route. The availability and other applications of the transyt method are described. /TRRL/