§393.82 requires every CMV to be equipped with a speedometer indicating vehicle speed in miles per hour and to maintain accuracy of ±5 mph at 50 mph. The rule is short, but it is one of the easier findings for an inspector to cite — the inspector compares the dashboard reading against a calibrated source as the vehicle moves.
Severity weight
Severity weight 1 in the Vehicle Maintenance BASIC. Notice-level by SMS weighting, but the cite pairs poorly with any §392.2 speeding finding — an inspector who finds both will note that the driver had no working means to know the speed.
How it gets cited
The common pattern is a non-functioning speedometer driven by a failed sensor, a bad cluster, or a CAN-bus fault — the gauge sits at zero or buries the needle. Less common: a working gauge that reads 5+ mph off after a tire-size change without recalibration.
How to prevent it
- After any tire-size, gear-ratio, or transmission swap, recalibrate the speedometer.
- Treat a dead speedometer as a same-day repair, not "we'll get to it" — drivers cannot self-regulate speed without it.
- Verify speedometer accuracy at every §396.17 annual inspection.
How Roadworthy HQ helps
§393.82 findings link to the vehicle record and the §396.9(d)(3) repair certification, so the calibration fix and the inspection that cleared it are documented in the audit binder together.