Synthesis of Safety for Traffic Operations - Transports Canada

Introduction
In concluding this section on methods and metrics it suffices to state that:
• Crash occurrence and severity are the primary metrics of safety;
• Crash surrogates that are definitively linked to either occurrence or severity are
reasonable alternative metrics;
• The typical methods of determining the safety impacts of a particular traffic
operations or control strategy is to use either properly developed safety
performance functions (SPFs) or crash modification factors (CMFs);
• Different study methodologies have different inherent strengths and weaknesses
and are key factors in determining the reliability of the study results; and
• Transferability and validity of SPFs and CMFs need to be assessed by the
practitioner.
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