The US Department of Transportation requires carriers operating in interstate commerce to display their name and USDOT number on both sides of the power unit (cab or vehicle door) before putting them into service. The lettering must be bold and contrasting to the color of the surface the lettering is applied to. The minimum lettering height for USDOT compliance is 2". (Click here to order 2" USDOT lettering.). We recommend going as large as possible while remaining aesthetically pleasing to avoid any potential issues. To ensure USDOT compliance, you must...
Lettering height should be a minimum of 2" tall, which is the absolute minimum for the dot numbers to be visible from 50 feet away.
US DOT 2" Numbers For Your Semi Truck (1-Pair) Be sure You're Legal! Choice Of Color