Better Junction Control with Bus Priority

Abstract

The problem was to design a traffic light controller for a set of neigh- bouring junctions, which gives priority to incoming buses while ensuring a degree of fairness to the general traffic.
The team has developed three complementary approaches, that present different strengths and weaknesses and might be applicable in different junction configurations or traffic conditions:
1. A continuous-variable, discrete-time optimisation approach for de- termining the fraction of green time to give to each arm of a junc- tion during the next traffic light cycle, in order to minimise total weighted squared vehicle waiting times, with more weight on buses than on cars.
2. A piece-wise linear ordinary differential equation model of queue length dynamics on a junction arm, based on flux of vehicles into and out of that arm.
3. Adiscrete-variable,discrete-timeMarkovDecisionProcessapproach. The state of the system is comprised of vehicle queue lengths and the junction’s current stage. The action is to stay in the current stage or move to the next stage. An optimal policy minimises long run expected discounted weighted delay.