A study was conducted of 497 drivers injured in a motor vehicle accident and treated at a hospital. The objectives were to determine the incidence of alcohol and other drugs in their blood systems at the time of the crash and the role these drugs may have played in the accident. The sample was considered conservative with respect to alcohol/drug incidence since only drivers who consented to a blood sample analysis were included.
The results showed that fully 38% of the drivers had alcohol or some other drug in their systems; alcohol was found in 25%, tetrahydrocannibinol in 9.5% and tranquilizers in 7.5%. Ten per cent of the drivers had ingested two or more drugs. It was found that legally intoxicated drivers (BAC³10%) had the highest culpability rate (74%) followed by drivers with THC (59%) and drivers with lower alcohol levels (54%). The drugfree drivers in contrast had a culpability rate of 34% while the drivers with tranquilizers were judged culpable in 22% of their accidents.
Compared with the drugfree drivers, the alcohol-involved drivers were overrepresented in single-vehicle accidents and in the striking vehicles of rearend and head-on crashes. The "alcohol accident type" with the highest incidence (94%) of alcohol involvement was a single-vehicle crash between midnight and 6 AM in a business/commercial/industrial area.
The study confirms that alcohol continues to be a major highway safety problem, and it appears that marijuana may also be a problem. Among the recommendations are that "alcohol accident types" be developed for drunk driver detection and other uses, that driver-alerting countermeasures be developed, and that crash risks associated with prominent drugs be determined.