Bus preemption signal (BPS): An application of advanced public transportation system (APTS)
Publication Type
Original research
  • Khaled Ahmad Al-Sahili

With the emergence of Intelligent Transportation System (ITS) technologies, there has been a renewed interest in bus priority signalalization (BPS). At present, there is no model capable of simulating various BPS strategies and then restoring the original signal settings after bus preemption is awarded. The effect of providing the BPS treatment on the Washtenaw Avenue Corridor in Ann Arbor, Michigan was studied. The NETSIM graphic animation feature was used to detect the bus arrival and award preemption; then, the signal timing plan was manually restored to the original signal setting. The model was calibrated using field data and the sensitivity of the model to several variables was tested. The corridor's signal timing was first optimized using the TRANSYT-7F model. The green extension/red truncation with and without compensation, the skip phase with and without compensation, and the conditional preemption plans were evaluated. It was found that signal preemption disrupts traffic progression, and thus increases overall network vehicle and person delay. Results of preemption were analyzed on a cycle-by-cycle basis and over the entire simulation period. The most appropriate preemption plan for each intersection was determined. Bus travel time and delay were reduced when the optimal BPS plan was used. The BPS was tested under different network traffic volumes, different main to cross street traffic ratios for an isolated intersection, and signal preemption for carpools. It was found that maintaining progression is most critical under heavy traffic conditions. The traffic volume criteria that warrant signal preemption were established. There appear to be advantages to providing carpools with preemption capability up to between 5%-10% of the main street traffic volume. In any corridor there are likely to be random fluctuations in the traffic demand. This variation may be as large as the measured effect of BPS.

Transportation Research Part A 1997 | 31 | 1 | 68-69
Publisher Country
Publication Type
Both (Printed and Online)