This included initial testing of urine for drugs and blood for alcohol in 736 employees. Out of the 175 incidents, 24 percent (42 incidents) had at least one employee test positive for either drugs or alcohol. There were however, eight events in which employees tested positive for more than one substance or more than one employee tested positive. When the accidents involved fatalities (36), a higher proportion of drugs or alcohol positive events or both (40 versus 21 percent) was found. In 11 of the 32 fully investigated drugs or alcohol-positive events involving 14 employees, the investigative agencies, the Federal Railroad Administration or the National Transportation Board (NTSB) determined that substance use was a probable cause or a factor relating to the accident. Cannabinoids, ethanol, cocaine, or multiple-drug use were found in 5, 3, 3, and 3 of those employees, respectively. Detectable drug and alcohol use occurs among railroad employees, and occasionally, it has resulted in accidents. 4 tables and 34 references (Author abstract modified)