§392.3 prohibits operating a CMV when the driver's ability or alertness is so impaired by fatigue, illness, or any other cause that it is unsafe to begin or continue. The rule reaches further than HOS — a driver who is technically within hours but visibly impaired is still in violation.
Severity weight
Severity weight 10 in the Unsafe Driving BASIC — tied for the top of the table with §392.80 texting and §392.82 hand-held phone use. A single 392.3 citation moves the carrier's Unsafe Driving percentile materially.
OOS
The 392.3 placement-out-of-service is for 10 consecutive hours. The driver cannot resume driving until that period expires, and the carrier must document the corrective action.
How to prevent it
- Train drivers and dispatchers that "I'm fine" is not a defense at roadside — observable signs (slurred speech, swerving, falling asleep at a stoplight) are what officers cite.
- Build a no-questions-asked layover policy and pay for it. Drivers who can't afford to stop will drive impaired.
- Document medical conditions and medications in coordination with the §391.43 medical examiner; sedating prescriptions can be disqualifying.
How Roadworthy HQ helps
Roadworthy HQ logs §392.3 findings against the driver record, links to the §391.25 annual review, and surfaces the §385.337(b) corrective-action documentation an auditor looks for after an Unsafe Driving citation.