Research Papers

Road Safety through Network Screening and In-Service Road Safety Reviews at Signalized Intersections in the Town of Markham

Version 1
Date added June 6, 2010
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Category 2010 CMRSC XX Niagara
Tags Session 3B
Author/Auteur Ravi Bhim, Margaret Parkhill, Balendra Sinnadurai, David Porretta


Purpose: The purpose of this paper is to highlight the proactive safety management approach the Town of Markham has adopted in addressing road safety at signalized intersections. The Town utilized a network screening methodology to select intersections with the greatest potential for safety improvement. Selected sites were then reviewed in more detail to determine appropriate countermeasures to improve safety for all road users. The purpose of network screening is to identify and prioritize those sites that have promise for potential safety improvements, and therefore merit further investigation. Conducting detailed engineering studies of candidate improvement sites requires funds and resources, and it is important to focus available resources where the greatest benefits can be achieved. By implementing an efficient network screening procedure that will best identify “sites with promise” (i.e., those sites that would likely provide high safety cost-effectiveness among all candidate sites) the Town is now better equipped to focus their funds and resources effectively.
Method: Using collision, traffic volume, and intersection attribute data for all signalized intersections from 1995 to 2004, Safety Performance Functions (SPF) were developed. This network screening methodology, which uses the empirical Bayes (EB) approach, was used in ranking all signalized intersections with the greatest potential for safety improvement. The network screening resulted in a prioritized list of signalized intersections based on their Potential for Safety Improvement (PSI). The top ten signalized intersections from the network screening were reviewed in more detail following the “The Canadian Guide to In-Service Road Safety Reviews” (Transportation Association of Canada, 2003).
Results: Based on analysis of data collected during the in-service road safety reviews, several potential countermeasures were recommended which would improve safety for all road users. Potential countermeasures included: engineering measures such as traffic signal coordination, geometric improvements, protected signal phases; enforcement; and education programs. Countermeasures were described and Accident Modification Factors (AMFs) were provided when available. This paper provides more details on the network screening results, potential countermeasures and the Town’s implementation strategy.
Conclusions: The Town of Markham is one of the few municipalities in Canada to develop and apply such a quantitative proactive approach in addressing safety concerns at their signalized intersections. The Town is actively reviewing other innovative ways to address road safety. More municipalities should be encouraged to adopt such an economical and beneficial approach in addressing safety concerns on their road network. Road safety is being considered in most municipalities in Canada; however, the approach taken may not always be as defensible or cost-effective. Allocating funds and recourses to improve road safety needs to be efficient before the best results can be attained. Prioritizing locations for improvement based on quantifiably and statistically- defensible methods provides a more effective use of limited resources. This paper has outlined the proactive approach applied by the Town of Markham, which other municipalities can adopt into their annual works program.

Ravi Bhim, Margaret Parkhill, Balendra Sinnadurai and David Porretta