Synthesis of Safety for Traffic Operations - Transports Canada

Evidence-based Road Safety
7. Is there coherence of the evidence?
The results of the analysis should, in most cases, agree with what is generally
known about the treatment and with the likely etiology.
8. Is there corroborating experimental evidence?
Rarely possible in road safety, although potentially important human performance
studies may be used to further support causation. Driving simulators, surveys,
and human performance studies that measure crash surrogates with a definitive
link to crash causation or increased crash severity are examples of this type of
experimental evidence.
9. Can we find applicable analogy?
If the mechanism through which the treatment acts is analogous to some similar
treatment. For instance, the province of Ontario implemented “Community
Safety Zones” (CSZs) , which are sections of road that are identified by municipal
by-law, where the fines for moving violations are doubled. The CSZs are
identified on the street by rectangular black-and-white, regulatory signs posted at
the roadside. The effect of CSZs on travel speed is negligible [Forbes, 2002].
The lack of a cause-and-effect between CSZs and speed is further supported by
the analogy to speed limits and travel speed, where changes in the posted speed
limit (communicated to the motorist through a rectangular black-and-white
regulatory sign posted at the roadside) also fail to illicit a change in travel speed.
The application of these tests, and not just identifying a statistical relationship, are the
appropriate method of assessing a cause-effect relationship. Of course, there are
instances where not all of the tests will point the researcher in the same direction. In
instances of paradoxical results among the above tests the practitioner must use his/her
discretion in interpreting and applying the research to practical situations.
The Current State of EBRS
EBRS is scientific, and therefore knowledge-based. What has become apparent in the
preparation of this Synthesis is that the knowledge base with respect to the safety impacts
of traffic operations and control strategies is underdeveloped. This places the practitioner
in the uncomfortable position of having to make decisions based on incomplete
information. Until sufficient good quality research has been conducted and made
available to the practitioner, the practitioner will likely have to rely upon prejudice,
hunch, opinion, and guesswork (PHOG).
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