EXECUTIVE SUMMARY

Traffic operations practitioners are continually making decisions that impact on the safety performance of the transportation network. In order to make the best possible decisions the practitioner must be aware of the best available evidence on safety. The trouble is that the road safety knowledge base is expanding and it is difficult for the practitioner to keep abreast of the conventional wisdom. Moreover, once found, critically appraising, and determining the usefulness of safety-operations research is a daunting task. Practitioners are in need of a document that synthesizes the safety impacts of various traffic operations and control strategies for their day-to-day use. This Synthesis is intended to serve that purpose. It contains information on the safety impacts of traffic operations and control strategies that are most urgent/useful to practitioners, and attempts to highlight the conditions in which the impacts are likely to be realized.

The overarching goals of this Synthesis are to promote evidence-based road safety (EBRS) among the Canadian transportation sector, and to help Canada achieve its objective of making Canadian roads the safest in the world. EBRS is the conscientious and judicious use of current best evidence in providing road safety for individuals, facilities, and transportation systems. 

Mindful of the above goals, the Synthesis was developed with the following objectives:

• Focus on traffic operations and control strategies; 
• The target audience is practitioners and other transportation professionals that make decisions and recommendations respecting traffic operations and control strategies; 
• Include research and studies that report on crash occurrence, crash severity, or crash surrogates with a proven correlation to crashes; and
• As much as possible synthesize Canadian research using Canadian datasets. 

This last objective proved to be overly optimistic. At the start of the project it was believed that practitioners had a vast storehouse of traffic safety research that was unpublished. As it turns out, this is not the case. While certainly some information is unpublished and residing in government files, it appears that mainly due to human and financial resource limitations, practitioners are not undertaking evaluations.

In order to identify the issues and information that would be most valuable to Canadian practitioners, a technical advisory team comprised of provincial and municipal transportation engineering professionals from across Canada was assembled and consulted. The subject matter of this Synthesis was suggested by the advisory team. The main topics presented herein are:

• Intersection control including signalization, all-way stop control, intersection control beacons, signal timing, and traffic signal design and operation;
• Traffic signs;
• Pavement markings;
• Pedestrian safety;
• Bicycle safety;
• Legislation and enforcement;
• Turn lanes; and
•  Traffic calming.

Literature synthesized in this document was gained through the following means:

• Conventional literature searches of known databases;
• Internet search using appropriate key words; and
• Personal contact with Canadian academics and road safety practitioners.

This Synthesis attempts to provide the reader with pertinent information concerning the parameters of the research, and the limitations of the study so that a critical appraisal is possible. In this way the practitioner is better able to judge whether the safety impacts identified are applicable to their particular situation. The key elements of the critical appraisal included a review of how the sites were selected for treatment, the treatment used¸ the study methodology employed, and the results. 

In many instances the documented research relating safety to traffic operations and control is not fully reported. That is to say, the results are available, but all of the information necessary to critically appraise the findings is not always available. The primary shortcoming of reported research is the lack of information on site selection procedures. It is well known that evaluation of crash countermeasures that have been implemented at sites selected because of a high incidence of crashes will overestimate the countermeasure effectiveness. A failure to report the site selection process/criteria will leave the practitioner with a deficiency in information. 

It is generally accepted that the appropriate metric for road safety is motor vehicle crash (MVC) occurrence and severity. Therefore, only research that assesses the impacts of a particular treatment on MVC occurrence and/or severity are included in the Synthesis. Research that used MVC surrogates are also included if the surrogate has been demonstrated to correlate well with MVCs. This action expands the available literature and remains true to the goal of promoting evidence-based road safety. In the end, operating speed, and traffic conflicts were the two surrogates that have definitive links to MVC occurrence or severity, and are included in the Synthesis.

As the road safety knowledge-base is continually growing, it is important that the practitioner have an understanding of how to appraise new evidence and integrate the findings with those contained herein. To this end, appendices have been provided on evidence-based road safety, critically reviewing literature, and the proper use of safety performance functions. In hopes that practitioners will be encouraged to conduct and document their own research, a further appendix is provided on conducting and authoring research.

Finally, readers should exercise caution in applying the results contained in this Synthesis to situations under examination. Apart from the critical review for methodological flaws in the research, readers must also consider the limitations of transferring research conducted in one jurisdiction to another jurisdiction. Specially, differences in crash reporting, crash severity classifications, driver populations, the vehicle fleet, road system legislation, and design standards may limit the applicability of the reported results to the jurisdiction in which the research was performed.

How to get the full report:

The full report on the Synthesis Of Safety For Traffic Operations is available in a printable format (733 KB).

To view PDF documents you must use Adobe® Acrobat Reader. Visit the Adobe site to download the latest, free version.

If you need an alternative format or for more information, please contact us by e-mail at RoadSafetyWebMail@tc.gc.ca or call toll free 1-800-333-0371 (Ottawa area (613) 998-8616).