Optimising traffic signal settings for periods of time-varying demand

When traffic demands are different in successive time periods, the signal settings that are optimal for each individual period are only local solutions to the problem. These settings may be readjusted and the changes between them shifted in time so that the overall performance for those periods taken together is improved. A sequential optimisation technique has been developed to minimise the total junction delay over the successive periods taken together by searching for the optimal signal timings and the time-shifts subject to certain queue length considerations, and each traffic stream in the junction can be undersaturated or oversaturated during a time period. Some example calculations are given and the results show that such a technique can provide modest improvements in the junction control performance and give less delay than the exisitng methods that optimise only for individual periods.