Head lamps are required equipment under §393.11(a)(1) and Table 1 — two, white, on the front at the same height, an equal number on each side of the vertical centerline, between 22 and 54 inches above the road — and §393.24 sets the standard. Under §393.24(a), every bus, truck, and truck tractor must be equipped with headlamps that provide an upper and a lower beam distribution of light, selectable at the driver's will, and steady-burning; the lamps must be marked in accordance with FMVSS No. 108. Auxiliary driving lamps and front fog lamps may be used in conjunction with the required headlamps but never in place of them (§393.24(a)–(b)). Headlamps must be mounted and aimable in accordance with FMVSS No. 108 (§393.24(c)) and aimed to its specifications (§393.24(d)). §393.9(a) then requires every required lamp to be capable of being operated at all times — the paragraph a dark head lamp is actually cited under.
A note on this page's address: an earlier version filed head lamps under §393.25. That section's own heading is "Requirements for lamps other than head lamps." The old address now redirects here.
OOS
Inoperable head lamps when the vehicle is operated at night are an out-of-service condition under the CVSA North American Standard Out-of-Service Criteria; the vehicle may not continue until the head lamp is repaired. The criteria are a CVSA publication updated each April 1, not a CFR section.
Severity weight
Severity weight 6 in the Vehicle Maintenance BASIC — high for a lighting finding, because a head lamp failure removes the driver's own forward visibility rather than the vehicle's visibility to others.
How to prevent it
- Make head-lamp verification a pre-trip non-negotiable, including the upper-beam check — §393.24(a) requires both beams, selectable by the driver.
- Replace head lamps in pairs even when only one has failed; the second failure usually follows within weeks.
- Re-aim to FMVSS No. 108 after any front-end repair (§393.24(d)).
How Roadworthy HQ helps
§393.24 / §393.9 head-lamp findings logged in Roadworthy HQ link to the vehicle and hold the vehicle until the §396.9(d)(3) repair certification is on file, alongside the DVIR that reported the defect (§396.11(a)(1)(iv)).