Study Details

Study Title: Safety Effects of Transit Signal Priority Using the Full Bayesian Approach

Authors: Ali et al.

Publication Date:JAN, 2021

Abstract: Transit signal priority (TSP) is a strategy that prioritizes the movement of transit vehicles through a signalized intersection to provide better transit travel time reliability and minimize transit delay. Although TSP is primarily intended to improve the operational performance of transit vehicles, it may also have substantial safety benefits. This study explored the potential safety benefits of the TSP strategy deployed at various locations in Florida. An observational before-after full Bayes (FB) approach with a comparison-group was adopted to estimate the crash modification factors (CMFs) for total crashes, rear-end crashes, sideswipe crashes, and angle crashes. The analysis was based on 12 corridors equipped with the TSP system and their corresponding 29 comparison corridors without the TSP system. The deployment of TSP was found to reduce total crashes by 7.2% (CMF = 0.928), rear-end crashes by 5.2% (CMF = 0.948), and angle crashes by 21.9% (CMF = 0.781), and these results are statistically significant at a 95% Bayesian credible interval (BCI) except for the rear-end crashes. On the other hand, sideswipe crashes increased by 6% (CMF = 1.060) although the increase was not significant at a 95% BCI. Overall, the results indicated that TSP improves safety. The findings of this study may present key considerations for transportation agencies and practitioners when planning future TSP deployments.

Study Citation: Ali, M.S., A.E. Kitali, J.H. Kodi, P. Alluri, and T. Sando. "Safety Effects of Transit Signal Priority Using the Full Bayesian Approach". Presented at the 100th Annual Meeting of the Transportation Research Board, Paper No. 21-03950, Washington, D.C., (2021).

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Transit

Countermeasure: Implement transit signal priority

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.9287.24 StarsAllNot specifiedUrban
0.9485.23 StarsRear endNot specifiedUrban
1.06-63 StarsSideswipeNot specifiedUrban
0.78121.94 StarsAngleNot specifiedUrban