Prepared by:

Alireza Hadayeghi, Ph.D. (Candidate)
Manager, Transportation Safety Systems
Synectics Transportation Consultants Inc. / University of Toronto


Brian Malone, P.Eng., PTOE
President
Synectics Transportation Consultants Inc.

Roger De Gannes, BSc., MSc., P. Eng.
Traffic Signals Engineer
Ministry of Transportation Ontario, Traffic Office

Abstract
Traffic signals, if properly designed and justified according to current engineering practice, can improve the traffic safety and traffic operations at intersections. The effects of resulting crashes and the impacts on safety from installing traffic signals at unsignalized intersections are complicated and the current literature and research on this topic is limited even though traffic signals have been used for many years. The current crash warrants in the Ontario Traffic Manual Book 12-Traffic Signals do not take into consideration the effect of traffic volume variations in crashes. It states if conditions such as "Five or more “correctable” crashes per 12 month period averaged over a 36 month period" are satisfied, a signal may be warranted. The purpose of this paper is to develop and recommend a safety analysis and evaluation tool for estimating the expected safety of installing traffic signals using the historical crash and volume data. It also provides a quantitative process tool for determining whether or not a traffic signal is justified at an unsignalized intersection. The proposed approach uses the Empirical Bayes method and crash prediction models for estimating the safety effects of unsignalized intersections, which are being considered for traffic signal installation. The performance of proposed procedure will be evaluated and analyzed on 17 unsignalized intersections taken from different jurisdictions in the province of Ontario, Canada.

For a complete copy of this paper, please contact: jsuggett@synectics-inc.net