There are six general times 
when it is mandatory for a motor carrier to drug test a driver, or other employee in a safety-sensitive position:
- Before hiring—the driver must always be tested unless he or she has been in a federally-approved drug testing program in the past 30 days and meets other strict requirements.
- After a collision—the driver must be tested in all instances when there has been a death and in some cases when there have been injuries or a towed vehicle.
- Randomly—all motor carriers must have random drug testing of 50% of its drivers annually.
- Reasonable suspicion—all carriers must drug test drivers it has a reasonable suspicion violate drug regulations.
- Return-to-duty—all drivers must receive a return-to-duty drug test.
- Follow-up—Follow up tests must meet federal requirements.
These drug tests are all mandated by Part 382, Subpart C of Title 49 of the Code of Federal Regulations.
