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General Knowledge · Alcohol, Other Drugs, and Driving

What is the federal rule on alcohol use while a driver is on duty, operating, or in physical control of a commercial motor vehicle, separate from the 4-hour pre-duty rule?

1.No alcohol use, being under its influence, or having any measured or detected alcohol concentration at all is allowed; this is a zero-tolerance standardCorrect answer
2.A driver may have a blood alcohol concentration of up to 0.04 while on duty, the same limit that is used in the federal testing program
3.The rule only applies while the vehicle is actually moving, not while it is stopped or the driver is otherwise on duty somewhere around the terminal yard
4.The rule applies only to drivers who hold a Class A commercial license, not to drivers who hold a Class B or Class C license

Explanation

While on duty, operating, or in physical control of a commercial motor vehicle, 49 CFR 392.5 prohibits alcohol use, being under its influence, or having any measured or detected alcohol concentration at all, a stricter, zero-tolerance standard than the 4-hour pre-duty window. The 0.04 figure is a real number, but it comes from the separate drug and alcohol testing program in 49 CFR Part 382, not from this section's flat prohibition, which is why it is a tempting but incorrect answer here. The other wrong options narrow the rule incorrectly: it is not limited to moments the vehicle is moving, since on duty and in physical control both count, and 392.5 names no license class, applying the same way to any person who operates a commercial motor vehicle.

Source: 49 CFR 392.5

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