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Evaluating the Safety Impacts of Countermeasures for Winter Weather Collisions


In Canada, winter weather is a fact of life, and one unfortunate consequence of our sometimes-snowy climes is weather related collisions. Based on geography and associate microclimate, certain highway corridors are particularly susceptible to weather conditions that complicate winter driving, and the result is a higher-than-expected concentration of winter-weather-related collisions.
One such location is the section of Highway 401 that passes through Northumberland County, in southeastern Ontario. In recent years, the Ministry of Transportation has implemented a number of countermeasures aimed at reducing the frequency of winter-weather-related collisions along this corridor. Included in those measures are warning messages on static and dynamic signs, snow fencing, and measures to prohibit highway access and communicate detours during weather-related highway closures.
As a Traffic Engineering Services Retainer assignment for the Ministry of Transportation of Ontario (MTO), IBI Group was asked to assess the safety effectiveness of the applied countermeasures. The assessment was conducted by means of an Empirical Bayes before-after study. In addition to providing an account of the safety effectiveness of the countermeasures in their current application, the assessment also attempted to develop collision modification factors (CMF) for the various treatments for future use.
Based on the available data and the types of countermeasures that were applied along the corridor, CMFs were initially developed to account for the aggregate impacts of all treatments at the project level. The analysis produced CMFs that suggest a 37% reduction in total collisions (40% reduction in fatal + injury collisions and 36% reduction in property damage only collisions) across the study corridor. Subsequent analysis produced CMFs that isolated the impacts of installing snow fencing. The results of that analysis suggest a 33% reduction in total collisions that is attributable to snow fencing alone. However, the specific micro-climate within the study area is such that it may amplify the benefits of the applied treatments, and were they applied elsewhere the countermeasures might not achieve the same effect. As a result, caution should be exercised in adopting the CMFs described herein for application in any other context.

Conference Paper Details

Session title:
Winter Road Maintenance - Getting You There Safely
Colwill, M.
Zhang, T.
Construction, Maintenance and operations