DOT lighting violations: what 49 CFR 393.9 and 393.11 require and how they count on your CSA score

A dead turn signal, a clearance lamp out, missing reflective tape: lighting is cited under a handful of federal rules, mainly 49 CFR 393.9 and 393.11, and every one of those violations lands in the Vehicle Maintenance BASIC of your CSA record. They do not all weigh the same. This guide quotes the rules word for word, shows which lamps are required on which vehicle, and explains how FMCSA’s Safety Measurement System (SMS) weighs each kind.

The rule, word for word

49 CFR 393.9 has two paragraphs:

• (a) Lamps operable.“All lamps required by this subpart shall be capable of being operated at all times. This paragraph shall not be construed to require that any auxiliary or additional lamp be capable of operating at all times.”
• (b) Not obscured.“Lamps and reflective devices/material required by this subpart must not be obscured by the tailboard, or by any part of the load, or its covering by dirt, or other added vehicle or work equipment, or otherwise. Exception: The conspicuity treatments on the front end protection devices may be obscured by part of the load being transported.”

The key word is required. Section 393.9 does not say every light on the truck must work. It says the lamps the subpart requires must work, and it says in so many words that an auxiliary or additional lamp does not have to.

Which lamps are required: 49 CFR 393.11

Section 393.11(a)(1) points to two sources. Table 1 of 393.11 lists the required lamps and reflectors by vehicle type. And “all commercial motor vehicles manufactured on or after December 25, 1968, must, at a minimum, meet the applicable requirements of 49 CFR 571.108 (FMVSS No. 108) in effect at the time of manufacture of the vehicle.” So the answer to “was this lamp required?” comes from Table 1 for your vehicle type and from FMVSS No. 108 as it stood when the vehicle was built.

Table 1 sorts vehicles into types, including:

• A: buses and trucks less than 80 inches wide;
• B: buses and trucks 80 inches or more wide;
• C: truck tractors;
• D: semitrailers and full trailers 80 inches or more wide, except converter dollies.

A few entries that decide common citations:

• Backup lamp.Table 1 lists it for types A, B and C: buses, trucks and truck tractors. It is not listed for trailers. Before treating a trailer backup-lamp citation as outside the rule, check FMVSS No. 108 for the trailer’s date of manufacture, which 393.11(a)(1) also applies.
• Parking lamps. Listed for type A only: buses and trucks under 80 inches wide.
• Rear license plate lamp.Footnote 11 to Table 1: “No rear license plate lamp is required on vehicles that do not display a rear license plate or on the rear of truck tractors while towing a trailer.”
• Identification lamps hidden by another unit.Footnote 3: “The identification lamps need not be visible or lighted if obscured by a vehicle in the same combination.” Section 393.25(b) says the same for lamp visibility generally: it does not apply “to lamps on one unit which are obscured by another unit of a combination of vehicles.”
• Combined lamps. The note to Table 1 allows lamps and reflectors to be combined (393.22 and FMVSS No. 108 S5.4), so one lamp can do two jobs, such as a side marker that also flashes as a turn signal.

Reflective tape: the trailer’s build date decides the section, not whether you need it

Section 393.11(b) requires a conspicuity system (retroreflective sheeting, reflex reflectors, or a combination) on each trailer 80 inches or more wide with a GVWR over 10,000 pounds “manufactured on or after December 1, 1993,” except pole trailers and trailers designed exclusively for living or office use. Trailers of the same size built before that date are covered by a different section, 393.13, which required them to be retrofitted (by June 1, 2001 for most trailers) and allows some alternatives to the red-and-white pattern.

So an older trailer is not exempt from reflective tape. If it has none, it is in violation of 393.13 instead of 393.11(b). A build date can show the wrong section was cited; it does not, on its own, show the trailer complied.

Prove the build date with the manufacturer’s certification label on the trailer or the state registration record. Do not rely on a model year from a VIN decoder. The VIN’s 10th character is a model-year code (49 CFR 565.15(d)(1)) and the same codes were used in earlier decades; the rule that lets a decoder tell the decades apart, an alphabetic 7th character, applies only to passenger cars, multipurpose vehicles and trucks of 10,000 pounds GVWR or less (565.15(b)). For a heavy trailer, the VIN alone can point to the wrong decade.

How a lighting violation counts: three different weights

In FMCSA’s current SMS input data, the lamp and reflector codes under 393.9, 393.11, 393.19, 393.24 and 393.25 are all in the Vehicle Maintenance BASIC, split across three violation groups:

• “Lighting”, severity 6: headlamps, turn signals, stop lamps, tail lamps, hazard warning signals, backup lamps, parking lamps, lamps of the wrong color, height or location, lamps not steady-burning, and mounting or aiming faults.
• “Clearance Identification Lamps/Other”, severity 2:clearance, identification, side marker and license plate lamps (inoperative, missing or obscured), and the general code 3939, “Inoperable Required Lamp.”
• “Reflective Sheeting”, severity 3: conspicuity sheeting and reflex reflectors.

The split is recent. Version 3.17 of the SMS Methodology (February 2024) moved 13 Vehicle Maintenance violations from the Lighting group to the Clearance Identification Lamps/Other group, as of the 23 February 2024 snapshot. A small number of rows in the data carry a severity of 1; that is consistent with the court-result rule, where a conviction on a different charge drops to 1 (see your ticket was dismissed in court), but we have not checked those rows one by one.

The rest works the same way as every Vehicle Maintenance violation:

• Out of service. A violation that put the vehicle out of service gets 2 more. See out-of-service violations and your CSA score.
• Same code, one count.Vehicle Maintenance uses violations from Level 1, 2, 5 and 6 inspections, and “in cases of multiple counts of the same violation, the SMS uses each violation cite only once per inspection.” Different codes count separately, and the total severity on one inspection in one BASIC is capped at 30.
• Time weight. Multiplied by 3 in the first 6 months, 2 from 6 to 12 months, 1 from 12 to 24 months. After 24 months it stops counting.

Worked example (a hypothetical inspection, arithmetic on the rules above).Three months ago an officer cited one rear turn signal inoperative (Lighting, 6) and two clearance lamps inoperative under the same clearance-lamp code (2, counted once). The inspection counts (6 + 2) × 3 = 24toward your Vehicle Maintenance measure. The one turn signal counts three times as much as both clearance lamps together. Fourteen months after the inspection the same pair counts 8 × 1 = 8.

Before you challenge: what a reviewer can act on

1. Was the lamp required on that vehicle?Find the vehicle type in Table 1 and the lamp’s entry, then the footnotes. Footnote 11 says no license plate lamp is required on the rear of a tractor towing a trailer, and 393.9(a) says an auxiliary or additional lamp need not work. Check what the report itself records about the unit: its type, and whether it was in a combination.
2. Does the code match what the officer wrote? If the description names a clearance or side marker lamp but the code is a turn-signal or stop-lamp code, the report contradicts itself and the correct code carries a third of the weight. Allow for combined lamps first: a side marker that also works as a turn signal can be cited as either.
3. Is it the right section? A trailer built before 1 December 1993 is covered by 393.13, not 393.11(b). That fixes the citation, not the missing tape.
4. Check the unit is yours. Match the VIN and plate on the report against your registrations and leases: an inspection on your record that isn’t yours.
5. Know what does not work. A receipt for a bulb replaced after the inspection shows you fixed it, not that it worked at the roadside. A report that simply leaves a detail out, such as which side the lamp was on, is not a contradiction: the reviewer can ask the officer.
6. File it properly, with the proof attached on the first submission: how to dispute a DOT violation and file a DataQ.

If the lamp was required, the code fits, and the report is accurate, a challenge will not remove the violation. It loses weight at 6 and 12 months and stops counting at 24.

Sources

• 49 CFR part 393, subpart B, Lighting devices, reflectors, and electrical equipment (eCFR, current to 8 October 2026): 393.9 (quoted in full), 393.11(a), (b) and Table 1 with footnotes 3 and 11 (last amended 91 FR 7873, 19 February 2026), 393.13(a), 393.25(b).
• 49 CFR 565.15, VIN content requirements (eCFR): (b) position 7 and (d)(1) the model-year code.
• FMCSA, Safety Measurement System (SMS) Methodology, Version 3.21 (methodology revised May 2026): Vehicle Maintenance BASIC (applicable violations and relevant inspections, one cite per inspection, OOS weight of 2, cap of 30, time weights); Appendix B, Table B-12 (393.9BRKLAMP, Lighting, severity 6) and the Version 3.17 change note (13 violations moved to Clearance Identification Lamps/Other, 23 February 2024).
• FMCSA, “SMS Input – Violation” dataset, data.transportation.gov: violation codes beginning 3939, 39311, 39319, 39324 and 39325, their descriptions, BASIC, violation group and severity weight, read 12 October 2026.