Attributable risk of alcohol and other drugs for crashes in the transit industry.

OBJECTIVE To estimate the impact of employee alcohol and drug use on crashes in the transit industry from 1995-2000. DESIGN Secondary analysis of federally mandated post crash and random alcohol and drug testing results. SETTING The US transit industry. SUBJECTS Transit industry employees. MAIN OUTCOME MEASURES Relative risk (RR), population attributable risk (PAR), and population attributable risk percentage (PAR%). RESULTS For alcohol testing, the estimated PAR% ranged from 0.02% (1999) to 0.03% (1995). For drug testing, the estimated PAR% ranged from 0.38% (1998) to 0.67% (1997). Based on these calculations, the estimated number of crashes per 1000 crashes attributable to alcohol was less than one during 1995-2000, and the number attributable to drugs ranged from about four to about six. The number of crashes attributable to either alcohol or drugs did not vary greatly from 1995-2000. Estimated rates of crashes attributable to alcohol or drugs were substantially lower in 1995, the first year of testing, than had been projected based on previous estimates, and did not show substantial change from 1995-2000. CONCLUSIONS Approaches to transit safety based on reducing employee use of alcohol and other drugs have modest potential for reducing number of fatalities, injuries, and crashes.