Effect of passenger presence on older drivers' risk of fatal crash involvement.

Objective: To determine the association between passenger presence and risk of fatal crash involvement in relation to driver and passenger age and gender, focusing especially on drivers ages 65 and older.

Methods: Data on US fatal crashes were obtained for 2002-2009. Using the quasi-induced exposure methodology, logistic regression analysis was used to predict the odds of fatal crash involvement as a function of driver age and gender as well as passenger age and gender.

Results: Overall, risk of fatal crash involvement with passengers was 43 percent lower for drivers ages 65-74 and 38 percent lower for drivers 75 and older. Older drivers' risk of fatal crash involvement was lower with almost all combinations of passenger age and gender; there was no reduction in risk with passengers ages 75 and older. Effects were stronger at nonintersection locations than at intersection locations.

Conclusion: Older drivers' crash risk is lower with almost every combination of passenger age group and gender. It is unclear whether the presence of passengers lowers older driver crash risk or whether safer drivers tend to ride with passengers.