DOT Decal Placement Guide

What the rule actually sets

For a commercial motor vehicle in interstate commerce, 49 CFR 390.21T sets three tests for the marking: it goes on both sides of the power unit (the tractor or straight truck), it contrasts sharply with the paint, and it is legible from 50 feet in daylight. The marking itself is your legal name or single trade name exactly as on your MCS-150, plus "USDOT" and your number, like USDOT 1234567.

The rule does not name a spot on the side or an inch height. Everything else on this page is shop practice from 20 years of lettering trucks, aimed at passing those three tests cleanly.

The usual spot: the cab doors

On most trucks we put the marking on the doors. They are big, flat, at eye level, and the same on both sides. Center the stack front to back in the flat area, below the window and above the lower body line, clear of the handle and mirror.

No room on the door? For New York carriers, NYSDOT's answer is the front fender of the power unit, never the trailer (NYSDOT DOT Number Q&A, Q15). See New York USDOT decals. On tractors with short doors, the cab side panel behind the door is another common choice.

Measure before you order

1. Measure the flat part of the door, width and height, between body lines, trim and the handle.
2. Use our rule of thumb: about 0.8 inch of width per character for every inch of letter height. USDOT 1234567 runs about 21 inches at 2 inches tall, 31 at 3, and 42 at 4. ACME HAULING LLC at 3 inches is about 38 inches.
3. If it will not fit, stack the name on two lines, or put USDOT above the digits.
4. Send a photo of the door with your order. The free proof shows the layout on it to scale before we cut.

Sizing is covered in more depth in USDOT number size requirements.

Layouts that work

• Stacked: name on top, USDOT line below. Fits most doors.
• One line: name and USDOT side by side. Works on long panels like a sleeper or box truck cab side.
• Narrow panel: USDOT on its own line above the digits.
• Extra lines: an MC number is optional under the federal rule (see USDOT vs MC number). A GVWR line goes below if your state calls for one. Unit numbers and phone numbers come last and smaller.

Our house minimum is 2-inch numbers and 3-inch names, so our USDOT number decals start at 2 inches. That is our practice for reading well at 50 feet, not a legal number. Keep the required lines the biggest things on the door.

Pick the color by the paint

• White, silver, light gray, yellow or cream truck: black lettering.
• Black, dark blue, dark green, dark gray or red truck: white lettering.
• Mid-tone paint: hold a black and a white sample on the door and step back. Use whichever reads first.
• Avoid silver on white, gray on silver and red on black. They look fine up close and disappear at a distance.

A simple self-check: in daylight, pace off about 50 feet and read the door. If you have to squint, change the color or go bigger.

Spots to avoid

• Door gaps and seams. Vinyl that crosses them gets cut and starts to lift.
• Rivets, ribs, deep body lines and tight curves.
• Anything that hides the marking: ladder racks, toolboxes, steps, fuel tanks.
• Old lettering. Take it off first. In California, on vehicles covered by the state's name-display rule, a previous owner's name has to be removed or covered within 60 days of an ownership change (CVC 27900(d)). Our old lettering removal guide shows how.

Match both sides

Measure from fixed points on each door, such as the bottom of the window and the rear edge, and use the same numbers on the other side. Tape a hinge across the top, check level, then apply. The full steps are in how to install truck decals.

Magnets follow different placement rules: flat steel only, off body lines. See magnetic vs vinyl.

Decals for this

Have your USDOT number, your exact MCS-150 name and a door measurement ready when you order.

• Custom USDOT Number Decals, from $16.00: the USDOT line, set of 2, cut to your door.
• Full Compliance Decal Kit, from $54.95: name, USDOT, MC and GVW cut to line up as one stack.
• Custom Truck Door Lettering, from $18.95: your company name line to sit above the number.