USDOT Number Display Requirements — Size & Location
If your truck needs a USDOT number, the federal rule for how to display it is short — but the details are the difference between passing a roadside look and getting a violation. Here is the whole rule in plain language.
Both sides of the vehicle · your legal name and USDOT number · in a color that contrasts with the background · readable from 50 feet away in daylight while the vehicle is stopped.
What must be displayed
Two things: the legal name or single trade name of the business that operates the vehicle — matching your MCS-150 registration — and the motor carrier identification number with “USDOT” in front of it, for example USDOT 1234567. Some states add their own lines on top: GVW, a state permit number, or the city and state. Check yours in our by-state table.
Where it goes
On both sides of the power unit. In practice that means the two cab doors — flat, painted, easy to letter, and where officers look first. A tractor pulling trailers marks the tractor, not the trailers.
How big it has to be
The rule is a legibility test, not a ruler: the marking must be readable from 50 feet in daylight while the vehicle is stationary. Most states and officers treat 2-inch letters as the height that passes, and that is the height our designer starts your lines at. Contrast matters as much as size — black on a white door, white on a dark wrap.
Decal, paint or magnet?
All three are legal. Cut vinyl is the standard because it stays put, stays sharp, and costs the least over its life. Magnetic signs are right for a personal truck that only works part-time — but the magnet must be on whenever the vehicle operates, and it needs regular care to avoid trapping moisture against the paint.
Common questions
Does the USDOT number have to be on both doors?
On both sides of the vehicle, yes. The cab doors are where nearly everyone puts it, but the rule is about the sides of the power unit being marked, not the door itself.
How big do the letters have to be?
The federal rule is written as a legibility test: readable from 50 feet away in daylight while the truck is parked. Most states and most enforcement officers read that as 2-inch letters, which is why 2" is the standard height we start you at.
Can I use a magnetic sign instead of a decal?
Yes — paint, vinyl decals and magnetic signs are all acceptable as long as the marking is on the vehicle and legible whenever it operates. If you run magnets, they have to be on the truck every time it moves.
What exactly has to be displayed?
Your legal business name (or a single trade name, as it appears on your MCS-150 filing) and your USDOT number, written with the letters USDOT in front of it.
Need the decals?
Type your USDOT number, pick your size and color, and see it on a truck door before you buy — or put your logo and your lines on one decal. Sold single or in pairs.
More USDOT guides: How to apply USDOT decals & magnetic signs · Care & cleaning of USDOT decals · Requirements in every state
Martin Graphics is a sign shop, not a regulatory agency. We publish this as a courtesy and keep it as accurate as we can, but rules change and enforcement varies. You are solely responsible for confirming and meeting the requirements that apply to your vehicle or vessel.
Lettering for the whole fleet
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