What 393.9H means in plain language
FMCSR 393.9H targets a straightforward but critical equipment failure: a head lamp on your commercial motor vehicle that doesn't work. The regulation requires that all lamps a vehicle is equipped with — including headlamps — must be operational and functioning as designed. If an officer walks up to your rig at a roadside inspection and one or both of your headlamps isn't lighting up, you're looking at a 393.9H citation.
This isn't a paperwork issue or an ambiguous judgment call. Either the lamp works or it doesn't. That's exactly why officers write this one up quickly and consistently — there's nothing to interpret. A burned-out bulb, a failed LED module, or a wiring fault that kills the lamp output is all it takes.
The practical takeaway: this violation is entirely preventable during a proper pre-trip inspection. If you're rolling out without confirming both headlamps are lit, you're accepting the risk of this citation every single time.
What our enforcement data actually shows
Across our database of 13 million+ inspections, 393.9H has generated 25,067 all-time citations and 15,467 citations in just the last 12 months — meaning more than half of all recorded violations for this code happened in the past year alone. In the last 90 days, officers wrote 3,194 citations under this code, confirming it remains a consistently active enforcement target.
Despite those volumes, the out-of-service picture is relatively favorable for drivers. Of 25,067 all-time citations, only 188 resulted in an out-of-service order — an OOS rate of just 0.7%. To put that in context, the all-FMCSR average OOS rate across all codes is 31.4%. At 0.7%, this code sits far below that average, which means in the vast majority of stops, you'll receive the citation and be allowed to continue operating. The code is classified as OOS-ineligible, which aligns with what the data shows in practice.
That said, the monthly trend data in our records shows a noticeable spike in OOS placements during December 2025 and January 2026, with 16 and 15 OOS orders respectively — elevated compared to most other months in the trailing 12. This code ranks #111 out of 3,036 FMCSR codes by citation volume nationally, placing it firmly in the top 4% of all cited regulations. Officers know this one. They look for it.
Who gets cited most
Looking at our inspection records from the last 180 days, Texas dominates the citation count by a wide margin — 6,068 citations in that window alone. North Carolina follows with 330 citations, and Iowa comes in third with 262 citations. These three states account for a significant share of recent enforcement activity under this code.
The OOS rate variation across states is worth noting. Texas sits at a 0.3% OOS rate on its 6,068 citations, while North Carolina runs 3.9% on its 330 citations, and Iowa is at 0.8% on 262 citations. That's a meaningful spread — the chance of being placed out of service for this violation in North Carolina is more than ten times higher than in Texas, based on our data. State-level enforcement discretion clearly plays a role in how this violation is handled after the citation is written.
Our data shows fleets such as EVANS DELIVERY COMPANY INC (USDOT 38111) with 53 all-time citations and CNC LOGISTICS S DE RL DE CV (USDOT 2726203) with 50 all-time citations appearing at the top of the carrier list for this code. High citation counts at the carrier level typically indicate a fleet-wide pre-trip inspection gap rather than isolated incidents.
On the equipment side, our records show Freightliner (FRHT) vehicles account for 8,238 all-time citations — the most of any make. Kenworth (KW) follows with 3,551 and Peterbilt (PTRB) with 2,998. If you're driving any of these platforms, your headlamp systems are among the most frequently flagged in the country.
How severe is this compared to similar codes
For perspective, compare 393.9H to its closest peers in the Vehicle Maintenance category. The broader 393.9(a) code — covering inoperable required lamps generally — has accumulated 660,737 citations with a 15.4% OOS rate. That's more than 26 times the citation volume of 393.9H and a dramatically higher OOS risk, reflecting how frequently lamp violations of all types are written and how seriously officers treat the broader category when multiple lamps are involved.
The related 393.9 code (Inoperable Required Lamp, a separate enumeration in our database) shows 180,097 citations and a 6.9% OOS rate — still nearly ten times the OOS rate of 393.9H at 0.7%. The more general the lamp violation, the more enforcement teeth it tends to carry.
For contrast, look at 393.11 (Lighting devices/reflectors), which has 179,734 citations but only a 1.8% OOS rate. That code and 393.9H operate in similar enforcement territory — high volume, low OOS risk — but 393.9H's 0.7% rate is even more favorable. The data is clear: a headlamp violation on its own is unlikely to park your truck, but it will go on your inspection record and feed into your carrier's BASIC scores.
How to avoid it
The co-occurring violation pattern in our 90-day data tells the real prevention story. Here's what to act on before every dispatch:
- Walk your headlamps every pre-trip, not just your marker lights. In our records, 393.9H shares 1,292 inspections with 393.9 (Inoperable Required Lamp) and 361 with 393.11 (Lighting devices/reflectors) — officers who find one lighting problem look for all of them. Check low beams, high beams, and confirm both sides.
- Check your turn signals at the same time. Our data shows 621 shared inspections with 393.9TS (Inoperative turn signal). If one lighting circuit is failing, related circuits are often next.
- Inspect your windshield. 791 shared inspections with 393.78 (Windshield condition defective) in just 90 days suggests officers writing lighting violations are also flagging cab-area defects. A cracked or obstructed windshield can accompany a headlamp citation in the same stop.
- Carry spare bulbs and fuses for your headlamp circuits. On Freightliner, Kenworth, and Peterbilt units — the three most-cited makes in our data — headlamp connectors and housings are known wear points. A spare sealed-beam or LED replacement module costs almost nothing compared to a citation.
- Don't overlook your brake system during pre-trip. 380 shared inspections with 393.47E (Slack adjuster defective) in 90 days shows that inspections catching headlamp issues often go deeper into the vehicle. Confirm slack adjusters and brake stroke on every pre-trip — an officer who finds a headlamp violation will keep looking.
- Verify your periodic inspection documentation is on the truck. 491 shared inspections with 396.17C (No proof of periodic inspection) in our 90-day data indicate that headlamp stops frequently escalate when paperwork can't be produced. Keep your annual inspection sticker visible and your documentation accessible.