Crash Modification Factors (CMFs) are...

• A. The ratio of the effectiveness of one condition in comparison to another condition
• B. A measure of weather severity
• C. A calibration factor to adjust data
• D. A step in safety management process

Answer: (A)

CMFs express how a safety condition changes crashes by comparing crashes under that condition to crashes without it, using the same exposure and time period. This ratio shows the condition’s effectiveness: a value below 1 means crashes are reduced, above 1 means crashes increase, and exactly 1 means no detectable effect. You apply the CMF to baseline crash estimates to predict the safety benefit of implementing the countermeasure (for example, a CMF of 0.75 suggests a 25% reduction in crashes). CMFs come from data or studies and describe the impact of a condition, not weather severity, a simple data calibration factor, or a step in the safety management process.