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How many hours before going on duty is a CMV driver banned from using alcohol?

4 hours.

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  1. 4 hours ✔
  2. 2 hours
  3. 8 hours

Why: Federal rules forbid using alcohol, or being under its influence, within 4 hours before going on duty or driving a CMV.

Huh, didn't know that: Carrying alcohol in the truck is also banned unless it is part of a manifested shipment or belongs to bus passengers.

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Why did the trucker sleep under the rig? To wake up oily.
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References

Answer: 4 hours. Federal rules forbid using alcohol, or being under its influence, within 4 hours before going on duty or driving a CMV.

  1. 49 CFR 392.5 Alcohol prohibition (eCFR) www.ecfr.gov/current/title-49/section-392.5
    within 4 hours before going on duty or operating, or having physical control of, a commercial motor vehicle
    Checked 2026-10-10.

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