According to FMCSA regulations, post-accident drug and alcohol testing of commercial motor vehicle operators is legally required when 1. It results in a human fatality, whether or not a citation is issued to the driver, 2. When an accident results in bodily injury to a party with immediate medical treatment away from the scene AND if a citation is issued to the driver, and 3. When a vehicle involved in the accident sustains disabling damage requiring towing AND a citation is issued to the driver. When drug and alcohol testing is arranged when it is not mandated, however, severe consequences could result if one of the tests turns out to be positive.