Knowledge CentreTechnical Resources SearchConference PapersAssessment of the Crash Modification Factors in the   Highway Safety Manual for use in Canada

Assessment of the Crash Modification Factors in the   Highway Safety Manual for use in Canada


The release of the Highway Safety Manual (HSM) can have a significant impact on the success of Canada’s Road Safety Vision successor plan for 2015 by enabling Canadian jurisdictions to benefit from the extensive research conducted during the compilation of the Manual. So an assessment of the applicability of this Manual in Canada is particularly timely. A major part of the HSM is a comprehensive list of Crash Modification Factors (CMFs), which is a compilation from past studies of the safety effects of various road treatments. The HSM implemented a very rigorous inclusion/exclusion process for reviewing the accuracy of the CMFs to determine their suitability for inclusion in the HSM. Part of the review, was to apply correction factors to any CMFs that were suspected of being subject to biases such as regression to the mean (RTM). This methodology is reviewed in this paper in the light of recent research on the extent of RTM bias. Then the CMFs listed in the HSM were compared to those currently used by Canadian jurisdictions. The results show that the CMFs included in Canadian manuals are similar to those in the HSM. However, it was identified that the HSM has CMFs for many other treatments not identified in Canadian manuals. Based on the rigorous inclusion process used by the HSM, these other CMFs can be assumed to be reliable and used for selecting safety treatments. However, it would be beneficial for the safety effects to be evaluated using the Empirical Bayes (EB) method to ensure the same change in collisions is achieved.

Conference Paper Details

Session title:
Bernard James
Yongsheng Chen
Bhagwant Persaud
Road safety