Which metric is most appropriate to assess whether a countermeasure achieved a crash reduction goal?

• A. CMF-based calculation using local data.
• B. Travel time savings.
• C. Fuel efficiency.
• D. Vehicle occupancy.

Answer: (C)

Assessing whether a countermeasure achieved a crash reduction goal should focus on safety outcomes, not mobility or efficiency. The most appropriate metric is a CMF-based calculation using local data. A CMF, or Crash Modification Factor, represents how the countermeasure is expected to change crash frequency. By applying the CMF to the baseline level of crashes (and accounting for exposure like traffic volume), you estimate the number of crashes that would occur after implementation. Then you compare this estimate to the actual observed crashes post-implementation. If the observed crashes are lower in line with the CMF, the countermeasure achieved its crash-reduction goal; if they’re higher, the goal wasn’t met. This method directly links the countermeasure to safety outcomes and reflects local conditions.

Travel time savings, fuel efficiency, and vehicle occupancy relate to mobility, energy use, or exposure but do not directly measure changes in crash risk, so they’re not appropriate for judging crash-reduction effectiveness.