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60041-1 Report Abstract

A Model to Evaluate the Impacts of Bus Priority on Signalized Intersection

Srinivasa R. Sunkari, Phillip S. Beasley, Thomas Urbanik II, and Daniel B. Fambro, Texas A&M University, August 1994, 60 pp.

The concept of providing bus priority at signals is not new. Numerous cities have implemented bus priority strategies at signals with varying degrees of success. Many of these cities have however discontinued using the priority measures. The advent of newer technology and an increased awareness for energy conservation and environmental problems due to emissions has prompted renewed interest in providing priority to buses at traffic signals. Reducing delay to the buses at signals can reduce overall travel time and improve schedule reliability.

This report documents the efforts to develop a model to estimate the impacts of providing priority to buses at signalized intersections. The existing strategies to provide priority to buses were reviewed. A priority strategy compatible with the local signal controllers was developed. A model using the delay equation in the 1985 Highway Capacity Manual was developed to simulate the intersection operations with bus priority. The priority strategy was implemented in a signal controller at an intersection in College Station. Bus arrivals were simulated and priority was provided manually.

Stopped delay data were collected for various scenarios of bus arrivals at the intersection when priority was provided. Data was also down loaded from the controller to obtain green split information. Volume data were obtained from video at the intersection. Stopped delay was obtained using the field data. Data were also input into the model and stopped delay values were obtained.

Delay values from the field were compared with the delay values obtained from the model. It was found that the model predicted delay very well at low v/c ratios but was slightly overestimating delays at high v/c ratios. The model can be used to estimate the impacts of implementing the priority strategy on intersection operation reasonably accurately.

The model can be a useful tool to traffic engineers to estimate the feasibility of implementing bus priority strategies. The model could encourage the increased use of bus priority measures. Better bus operations can lead to the bus being a viable alternative to the car. This in turn can lead to a reduction in vehicle miles of travel (VMT) and energy conservation, and improvement in pollution emissions.

Keywords: Bus Priority, Green Extension, Early Green, Compensation, Fuel Consumption

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Reference Report #60041-1