§393.13 requires every CMV to have operative stop lamps activated whenever the service-brake control is applied. Trucks and buses manufactured on or after March 7, 1989 also require a high-mounted brake lamp on tractors with a permanently attached body. The lamps must be visible from 300 feet on a straight, level road in normal daylight.
OOS criteria
All stop lamps inoperative (every stop lamp on the unit dark) is an OOS condition under the North American Out-of-Service Criteria. A single inoperative stop lamp is a roadside citation but generally not OOS by itself.
Severity
Severity weight 2 in the Vehicle Maintenance BASIC. The compounding risk is when §393.13 pairs with §392.7 (driver pre-trip failure) — both findings hit the BASIC.
How to prevent it
- DVIR includes a stop-lamp check at pre-trip and post-trip. §396.11(c) requires the driver review the prior DVIR before next dispatch.
- LED replacement lamps last longer and fail less abruptly than incandescent — common upgrade for owner-operators.
- Trailer-end stop lamps depend on the 7-pin cable. Inspect the cable connector at every coupling.
How Roadworthy HQ helps
Stop-lamp defects logged in a DVIR auto-link to the vehicle, surface as a maintenance task, and block the next dispatch under §396.11(c) until repair certification is filed. The audit binder retains both the DVIR and the repair documentation.