Road Safety Fundamentals
Concepts, Strategies, and Practices that Reduce Fatalities and Injuries on the Road

U.S. Department of Transportation, Federal Highway Administration

Performance Measure	Accounts for Traffic Volume	Accounts for RTM Bias	Accounts for Crash Severity
1. Average crash frequency	No	No	Not explicitly*
2. Crash rate	Yes	No	Not explicitly*
3. Equivalent property damage only (EPDO) average crash frequency	No	No	Yes
4. Relative severity index	No	No	Yes
5. Critical rate	Yes	No	Not explicitly*
6. Excess predicted average crash frequency using method of moments	No	No	Not explicitly*
7. Level of service of safety	Yes	No	Not explicitly*
8. Excess predicted average crash frequency using SPFs	Yes	No	Not explicitly*
9. Probability of specific crash types exceeding threshold proportion	No	Not affected by RTM bias**	Not explicitly*
10. Excess proportion of specific crash types	No	Not affected by RTM bias**	Not explicitly*
11. Expected average crash frequency with empirical Bayes adjustments	Yes	Yes	Not explicitly*
12. EPDO average crash frequency with EB adjustment	Yes	Yes	Yes
13. Excess expected average crash frequency with EB adjustment	Yes	Yes	Not explicitly*
* While these measures do not explicitly mention severity, analysts can adapt any of the measures to consider any severity level.		** These two measures will not be affected by RTM only if they are based on data from a long time period.