Objective. Impaired drivers and other high-risk road users are less likely to use their safety belts, thus increasing the risk of fatal injury in the event of a crash. Although safety belt laws have been shown to increase wearing rates for daytime non-crash-involved drivers and their front-seat passengers, little evidence is available on the effect these laws have on belt usage by crash-involved drinking drivers and their passengers.

Methods. This study evaluated the influence of primary safety belt law upgrades from secondary laws on front-seat occupants of passenger cars driven by drinking drivers in fatal crashes in five states: California, Illinois, Maryland, Michigan, and Washington. The outcome measures used to evaluate these law upgrades were (1) the change in safety belt usage rates of front-seat occupants in passenger cars driven by drinking drivers in fatal crashes and (2) the change in alcohol-related front-seat occupant fatalities in passenger cars driven by drinking drivers.

Results. Four of the five states demonstrated increases in safety belt use by front-seat occupants of passenger cars of drinking drivers in fatal crashes following the upgrade to primary safety belt laws. Three states (California, Michigan, and Washington) experienced significant reductions in the number of front-seat occupant fatalities in vehicles driven by drinking drivers.

Conclusions. The adoption of primary law upgrades was associated with significant increases in safety belt use (four of five states) and significant reductions in fatalities among high-risk occupants (i.e., front-seat occupants involved in fatal crashes in vehicles driven by drinking drivers) in three of the five states studied.