When considering implementation of multiple countermeasures at a problem location, how are the Crash Modification Factors treated?

When implementing multiple countermeasures at a problem location, Crash Modification Factors (CMFs) are treated as multiplicative factors. This approach reflects how the effectiveness of one safety measure can interact with the effectiveness of another. By multiplying the CMFs of the individual countermeasures, you can derive an overall effectiveness factor for the combination of measures.

This method assumes that the safety benefits from each countermeasure contribute in a non-linear fashion, where the combined effect is more than just a simple additive sum. For example, if one countermeasure reduces crashes by 30% and another by 20%, the combined reduction is not simply 50%; instead, their multiplicative effects account for the interaction and potential synergies between different countermeasures, yielding a greater overall reduction in crash likelihood.

In contrast, options that suggest adding these factors, stating they cannot be combined, or only using the most impactful one do not accurately reflect the established methodology in traffic safety engineering and the understanding of cumulative effects of safety measures. Therefore, multiplying the CMFs provides a more accurate depiction of the total impact when multiple countermeasures are applied at a given location.