Real time public transport priority

Abstract

Improving the effectiveness of transit signal priority operations has been the subject of considerable research and the results show that the unintended bus delay can be significantly reduced. A major controversy, though, is that these methodologies may bring excessive delays on non-prioritized junctions, as their assigned greens are shortened. Also, a very common dilemma appears is cases where two buses request priority from conflicting directions. In this thesis a real time public transport priority methodology is presented and evaluated. This methodology aims to change the signal plan locally in favor of a bus when this bus is detected and priority is requested. The strategy is based on rules while two different priority levels exist. Depending on the position of the bus and the current signal phase, the strategy chooses either to extend the green time or to reduce the red time of the bus. For conflicting priority requests a number of criteria must be taken into account in order to serve both requests, if feasible, otherwise in order to decide which bus should be served first. This strategy can be easily implemented at different road networks. Additionally, when a signal phase is modified for the implementation of a bus priority traffic plan, then it can be easily adjusted to the initial signal plan without affecting the rest of the network. The methodology is implemented in a microscopic simulation environment emulating a part of the urban network of Chania with realistic traffic conditions. The criteria used for the assessment of the methodology are the average delay time, the average harmonic speed and the CO emissions. It is shown that all the criteria for the buses are significantly improved without really affecting the rest of the vehicles in the network.