Risks older drivers pose to themselves and to other road users.

PROBLEM Studies have shown that older drivers have high death rates and lower rates of involvement in crashes that kill others; but most studies have not considered drivers' responsibility for their crashes, and many have considered only one particular measure of risk. METHOD This study examines risks that drivers of various ages pose to themselves and to others on per-driver, per-trip, and per-mile bases, taking responsibility for crashes into account, using United States fatal crash data from 1999 through 2003 and travel estimates from 2001. RESULTS Relative to other age groups, drivers aged 85 and older face the highest risk of their own death, whereas teens pose the greatest risk to passengers, occupants of other vehicles, and non-motorists. DISCUSSION The oldest drivers pose more risk to other road users than middle-aged drivers do; the degree of their excess risk depends strongly upon how risk is measured. IMPACT ON INDUSTRY These results demonstrate the importance of keeping clear the meaning and implications of various risk measures.