So you have been told that you need to install US DOT Numbers on your vehicle by either a police officer, state official, or inspector. Your first step is to apply for your US DOT Number with the US Department of Transportation. You can start by visiting https://www.fmcsa.dot.gov/registration.
Upon jumping through a few hoops, you will receive approval and be issued a US DOT number specific to your company. The US DOT will require you to display, at a minimum, both the company name the way it is listed on your registration and the US DOT number on both sides of your vehicle. They do require a 50’ visibility of the lettering. With the minimum 2” tall US DOT numbers and letters, you will be compliant. The lettering is fairly easy to install, but many of our customers do not want it on their vehicle permanently.
If your vehicle is made out of steel, you may want to consider a magnetic US DOT sign for your truck or van instead. The magnetic DOT number signs are removable and reusable and work great for registered companies that may use a personal vehicle for work from time to time, or only haul a few times a year.