Integrated Signal Control and Route Guidance based on Back-pressure Principles

Traffic signal control and route guidance are the oldest and most applied dynamic traffic management measures. Most of the time they operate in a local mode, although there is trend toward network-wide traffic management. For traffic signal control already several network systems existed, but so far the integration with route guidance is lacking. In this paper we describe a new strategy to integrate traffic signal control and route guidance, based on the principles of back-pressure control. The algorithms developed are tested in a theoretical network and it was shown that traffic signal control based on back-pressure control performs well. Using back-pressure for route guidance required some assumptions which are open for debate. The results show that the average density is not such a good measure for route pressure and that travel time as a pressure variable performs better. A combination of factors of pressure based on density and travel time seems to be the best choice. Using back-pressure for both signal control and route guidance gave promising results, although the differences with optimized local control were small. Future research is recommended on the fine-tuning of the back-pressure traffic signal model, and on further integration and coordination of the control strategies. On the part of route guidance, finding representative route pressure values and making the model applicable of larger networks requires more research.