Predictive–Tentative Transit Signal Priority with Self-Organizing Traffic Signal Control

Reducing bus delay beyond what can be achieved with conventional transit signal priority requires making and responding to longer-range predictions of bus arrival time, which include dwell time at an upstream stop. At the same time, priority decisions based on such uncertain predictions should be reversible if the dwell time should be much longer than expected. Rules for applying these concepts are proposed for application in the framework of self-organizing traffic signal control developed by authors Cesme and Furth. Predicted arrival time is based on a calculation of expected remaining dwell time and is compared with the earliest time the bus phase can be expected to return to green. One possible decision is to expedite return to green so that secondary extensions (a feature of self-organizing control logic) are inhibited. The other is to hold the green; however, this decision can be reversed if updated predictions of expected remaining dwell time indicate that the bus will arrive after the maximum green extension has expired. Simulation tests on a corridor with nine signalized intersections showed a 75% reduction in bus delay, to only 5 s per intersection, with only a 3% increase in general traffic delay.