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DMV Permit · License and Registration

At what blood alcohol concentration (BAC) does the law typically consider a commercial driver legally impaired?

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

0.04% — commercial drivers (CDL holders) are held to a stricter standard because they operate larger, more dangerous vehicles and drive professionally

  1. A 0.02%
  2. B 0.08% (same as non-commercial drivers)
  3. C 0.04% — commercial drivers (CDL holders) are held to a stricter standard because they operate larger, more dangerous vehicles and drive professionally
  4. D 0.10%

Why this is the answer

Commercial driver alcohol limits: BAC 0.04% is the legal limit for CDL holders operating commercial vehicles — half the standard adult limit of 0.08%.

Why stricter: Commercial vehicles weigh up to 80,000 lbs; stopping distances are much longer; the consequences of crashes are more severe; commercial drivers are professionals who have accepted greater responsibility.

Practical implications: A commercial driver who had two drinks with dinner and registers 0.04% BAC is legally DUI while driving their commercial vehicle — even though the same BAC is below the legal limit for their personal vehicle. This standard applies any time the CDL holder is operating a commercial vehicle.

CDL dui consequences: 1-year disqualification for first offense; lifetime disqualification for second offense or any offense in a CMV.

Source: DMV Handbook, Commercial Driver BAC Limit

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About this topic: License and Registration

License and registration questions cover graduated licensing stages and restrictions, carrying your license and registration, address-change deadlines, and the point system and suspension rules. This is one of 11 Rules of the Road questions on license and registration, each with a full explanation on a single study page.

New to this exam? Our DMV Permit exam guide explains the format, scoring, and how to prepare.

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