Research Papers

Evaluation of level-of-service and safety indicator of bicycle traffic light treatments at signalized intersections

Version 1
Date added June 26, 2017
Downloaded 0 times/fois
Category 2017 CARSP XXVII Toronto
Tags Research and Evaluation, Session 1B
Author/Auteur Bismarck Ledezma-Navarro
Stream/Volet Research and Evaluation

Slidedeck Presentation Only (no paper submitted)



Urban cycling has been on the rise across major North American cities including Portland, San Francisco, Washington D.C., and Montreal. However, this increase in cycling has led to greater conflicts with motorized traffic. 85% of all conflicts between cyclists and motorists occur at signalized intersections with high vehicle and bicycle traffic. Cities including New York and Montreal have used the elimination of certain turning movements, such as right-turn-on-red (RTOR) implemented in the 1970s, or the operation of exclusive protected or leading bicycle phases. Expanding on these ideas, the City of Montreal has implemented different signal phase strategies at signalized intersections, in an attempt to mitigate right turning collisions. Some of the treatments include partially protected phases, completed protected cyclist phases, and protected phases with turning vehicles permitted. The purpose of this study is to determine the impact of the leading and exclusive bike signal phases on vehicular traffic flow. More specifically, the objective of the research is to investigate the effects of alternative phasing strategies on different traffic flow, level-of-service, and safety indicators, such as bike delay, average vehicle queue and delay, time to collision and post-encroachment time. For this purpose, a microsimulation modeling approach is implemented using PTV VISSIM and SSAM from the FHWA. Four phasing patterns are tested at four different intersections with 156 different traffic flow scenarios. Each simulation is run 10 times and then the mean of the various flow and safety indicators is obtained. A python script was developed to automatically run the VISSIM simulations, which were analyzed manually in SSAM. Though this research is currently ongoing, this work should show the improvement of the leading cyclist phase on both safety indicators and level-of-service compared to intersections with non-prioritized signal timing schemes. The simulations will be used to compare each of the traffic light phases with a non-prioritized scenario. A series of charts will be developed to aid in selecting the traffic signal design that minimizes delay and/or conflicts for a given flow and intersection geometry. One of the drawbacks of the methodology is the reliability of the simulations. Although simulations have shown positive results, VISSIM assumes an ideal conflict scenario in which motorized users behave respectfully towards other users. With that in mind, several parameters and characteristics of the network are adjusted in order to account for certain user violations. Simulations of leading traffic light phases have shown a positive effect as on improving the level of safety and reducing motorized vehicle delay. Historically, this signal strategy has shown positive results when implemented for pedestrian protection and has the potential to improve cyclist safety without generating a great impact on driver delay.

Bismarck Ledezma-Navarro