Everybody calls it DOT tape. The regulation calls it a conspicuity system, and the difference matters, because the rule is not "put reflective tape on your trailer" — it is a specification with a width, a segment length, a coverage fraction, a height band and a stamped grade marking, and a vehicle either meets it or does not.
It is also narrower than most people think. Below is what 49 CFR 393.11 actually reaches, what the sheeting has to be, and the one number that circulates constantly and is not in the regulation at all.
Who the rule covers — and who it does not
The conspicuity requirement in 393.11 reaches two categories of vehicle, not one:
- Trailers with an overall width of 2,032 mm (80 inches) or more and a GVWR over 4,536 kg (10,000 pounds), manufactured on or after 1 December 1993 — except pole trailers and trailers designed exclusively for use as offices or dwellings.
- Truck tractors manufactured on or after 1 July 1997.
That is the whole list. Read it twice, because the omission is the useful part: a straight truck or a box truck is neither a trailer nor a truck tractor, so the red-and-white conspicuity treatment does not apply to it.
This is where a lot of well-meant advice goes wrong in the other direction, so be precise about what the exemption is not. A straight truck is still fully covered by the rest of 393.11 — the lamps and reflex reflectors laid out in the section's Table 1. FMCSA publishes a dedicated straight-truck illustration showing exactly which lamps and reflectors go where. The accurate statement is that a box truck needs its Table 1 lamps and reflectors and does not need the FMVSS 108 red-and-white conspicuity treatment. It is not "box trucks need nothing reflective".
What the sheeting itself has to be
The material specification lives in FMVSS No. 108 (49 CFR 571.108), which 393.11 incorporates by reference. Note a numbering quirk if you go looking: FMVSS 108 was reorganised in 2007 and the conspicuity requirements now sit at S8.2, but 393.11 and 393.13 still cross-reference the old S5.7 numbering. Both point at the same requirements.
| Property | Requirement |
|---|---|
| Pattern | Alternating red and white segments on the sides and rear of a trailer and on the rear of a truck tractor; white only at the upper rear corners |
| Segment length | 300 mm, with a tolerance of ±150 mm — so 150 to 450 mm per segment |
| Sheeting width | 50 mm (Grade DOT-C2), 75 mm (DOT-C3) or 100 mm (DOT-C4) |
| Grade marking | The letters DOT-C2, DOT-C3 or DOT-C4 on every white or red segment, at least 3 mm high, permanently stamped, etched, moulded or printed in indelible ink |
| Material standard | ASTM D 4956-90 Type V sheeting, except for the photometric requirements, which FMVSS 108 sets itself |
| Clearance from lamps | The edge of white sheeting must not sit closer than 75 mm to the lens of any required lamp |
The grade stamp is the practical one. An inspector does not need a photometer to tell whether the tape on your trailer is conspicuity-grade material or something bought by the roll at a hardware store — they read DOT-C2 off the segment. Unmarked tape is not compliant no matter how bright it looks.
Where it goes
Sides: the strip does not have to be continuous. What it has to do is add up. The segments together must cover at least half the length of the trailer, with the spaces between them distributed as evenly as practicable, and each portion mounted as horizontal as practicable. The centreline of the strip belongs between 375 mm (15 inches) and 1,525 mm (60 inches) above the road surface, measured unladen — or as close to that band as practicable where the body will not allow it.
Lower rear: a horizontal bar across the full width of the trailer, as horizontal as practicable, starting and ending as close to the extreme edges as practicable.
Upper rear corners: two pairs of white strips, each strip 300 mm (12 inches) long, one horizontal and one vertical per corner, as close to the top of the trailer as practicable and as far apart as practicable.
A truck tractor is different geometry and worth its own line: the rear of a tractor takes two strips 600 mm long in alternating red and white, mounted as horizontal as practicable and as far apart as practicable.
The measurement everyone quotes that is not in the rule
Search for conspicuity requirements and you will find the phrase "as close as practicable to 50 percent of the length" on page after page. It appears on vendor sites, on trade-association handouts, in forum posts. It does not appear in the Code of Federal Regulations.
What the regulation says is that the segments must add up to at least half the trailer's length and that the gaps must be distributed as evenly as practicable. The "as practicable" qualifier attaches to the spacing, not to the coverage. Half is a floor, not a target you aim near. If somebody is telling you that 45 percent coverage is close enough to practicable, they are quoting a paraphrase back at you.
The same qualifier does legitimately attach to the mounting height. NHTSA has interpreted the 15-to-60-inch band as "as close as practicable to" that range, precisely so a manufacturer does not have to modify a body to hit it. Height has give. Coverage does not.
Trailers built before December 1993
Older trailers are handled by a separate section, 49 CFR 393.13, which required carriers to retrofit trailers and semitrailers built before 1 December 1993 that are 80 inches or wider with a GVWR of 4,536 kg (10,001 pounds) or more. Offices and dwellings, pole trailers and driveaway-towaway movements are excluded. The retrofit deadlines are long past — 1 June 2001 for most trailers, 1 December 2001 for container chassis. The allowance for colours other than red and white on the sides and lower rear expired on 1 June 2009, so red-and-white is the operative pattern today.
One caveat with a date on it. In May 2025 FMCSA proposed to rescind 393.13 outright, on the reasoning that every trailer it touches is now more than thirty years old. The comment period closed in July 2025. As of writing, 393.13 is still a live section and no final rule has issued — but if you are reading this some time after publication, check the docket before relying on either answer. The proposal is explicit that trailers built on or after 1 December 1993 would still have to maintain their sheeting regardless.
Worn, dirty and damaged tape
There is no percentage in the regulations. No minimum retained brightness, no "more than X inches missing", no maximum number of dead segments. People look for that threshold constantly and it does not exist.
What exists is two qualitative duties. Part 393 requires that lamps and reflective devices not be obscured — by the tailboard, by the load or its covering, by dirt, by added equipment, or otherwise. That is the clause that reaches a filthy trailer. And 49 CFR 396.3 requires every carrier to systematically inspect, repair and maintain the vehicles under its control. Between them, the judgement about whether your tape still counts belongs to the inspector standing next to it.
On the enforcement side, CVSA's operational policy confirms conspicuity is documented as a violation coded 393.11S, and that missing treatment on one or both sides of a post-1993 trailer is recorded as a single violation rather than one per gap. Whether it also puts a vehicle out of service is set by the North American Standard Out-of-Service Criteria, which CVSA sells rather than publishes — we have not read the current edition and will not guess at it here. Treat it as a citable violation that feeds your Vehicle Maintenance BASIC and worth fixing before it is written up.
Does reflective vinyl help your USDOT numbers?
People ask us this constantly, usually assuming reflective lettering is somehow more compliant. It is not — and it is not less compliant either. 49 CFR 390.21T sets a performance standard for markings: letters that contrast sharply with their background and are readily legible from 50 feet in daylight while the vehicle is stationary. Material is not mentioned. Reflective vinyl is neither required nor prohibited.
Note what the test is, though. It is a daylight test at a standstill. Retroreflectivity does nothing for it, because retroreflective sheeting works by returning a headlight beam to its source and there is no beam at noon. Reflective door numbers are a preference — some owners like how the truck reads at a dock at night — not a compliance upgrade. Anyone selling them as "DOT approved" is selling you a phrase that does not exist.
Does my box truck need red-and-white DOT tape?
Not under the federal conspicuity rule. 49 CFR 393.11 applies the conspicuity treatment to trailers 80 inches or wider with a GVWR over 10,000 pounds built on or after 1 December 1993, and to truck tractors built on or after 1 July 1997. A straight truck is neither. It does still need the lamps and reflex reflectors that Table 1 of the same section requires, and state law is a separate question.
Can I use any reflective tape, or does it have to be a specific product?
It has to be conspicuity-grade sheeting meeting FMVSS No. 108, and you can check that without any equipment: every red or white segment carries the letters DOT-C2, DOT-C3 or DOT-C4 at least 3 mm high, permanently marked. Tape without that stamp does not comply regardless of how bright it is.
How much of the side has to be covered?
The segments do not have to be continuous, but together they must cover at least half the length of the trailer, with the gaps spread as evenly as practicable. Half is a minimum. The widely quoted phrase "as close as practicable to 50 percent" is a paraphrase that circulates on vendor sites and is not regulatory text.
My tape is faded and a few pieces are missing. Is that a violation?
There is no numeric threshold in the regulations — no percentage of brightness or number of missing segments. What the rules require is that reflective devices are not obscured, including by dirt, and that the carrier systematically maintains the vehicle under 49 CFR 396.3. The call belongs to the inspector, which in practice means faded or patchy tape is worth replacing before it is written up.
Do reflective USDOT numbers count for anything?
Only aesthetically. The marking rule at 390.21T asks for sharp contrast and legibility from 50 feet in daylight while stationary — a daylight test, which retroreflectivity cannot help with. Reflective lettering is permitted, is not required, and is not a compliance feature.
If you need it done
We cut and apply DOT-C2 conspicuity tape at the shop in Rolling Meadows along with USDOT and MC number sets and trailer lettering. If a strip has been peeling since spring, bring the trailer in — a lower rear bar and two upper corners is a short job, and it is a cheaper morning than the one that starts at a scale house. Call or text 224.400.0950.