Knowledge CentreTechnical Resources SearchConference PapersLessons Learned from Adopting the Highway Safety Manual to Assess the Safety Performance of Alternative Urban Complete Streets Designs

Lessons Learned from Adopting the Highway Safety Manual to Assess the Safety Performance of Alternative Urban Complete Streets Designs


A safety assessment of street designs is an essential stage in the planning process of future transportation systems. Such an assessment guides decision-makers in selecting the safest and most sustainable design options. In this study, the Highway Safety Manual (HSM) predictive methods were used to assess the associated safety risks of alternative Complete Streets designs drafted by the City of Edmonton. The City proposed a total of 63 (42 collector, 12 local, and nine arterial road) design drafts. For each of the design proposals, the safety indices were computed and alternative options were compared. The objective of this paper is twofold: i) assess the safety performance of those alternative design drafts; and ii) highlight the lessons learned as well as the issues and challenges faced while using the HSM predictive methods to conduct the assessment. The results obtained from the safety assessment reveal that road cross sections with a large lane width, a large offset of a roadside fixed object, the presence of a median, no on-street parking, and no on-street bike lane have less safety risks compared to road cross sections that do not possess these features. As for the second objective, several issues and challenges were faced: i) unavailability of baseline models for certain site types (e.g., six-lane divided arterial) and roadway
categories; ii) difficulties in finding appropriate crash modification factors (CMFs) for some geometric road features; iii) debatable credibility of some of the CMFs as a result of regional factors (e.g., weather, terrain, etc.); iv) the fact that some CMFs were only developed for certain roadway categories or collision severities, while others do not specify the roadway category; thus, using these CMFs is based on assumption; and v) the number of CMFs used to adjust each base model exceeded three, which affects the accuracy of the predicted number of collisions. These issues and challenges may provide a future research direction to enhance the scope of the HSM. Furthermore, the assessment process illustrated herein can be proactively used during roadway planning and design to compute the associated safety risk of different Complete Streets cross sections.

Conference Paper Details

Session title:
Road Safety Policy Development - Past, Present, Future
Barua, S.
El-Basyouny, K.
Islam, T.
Gargoum, S.
Road safety