Any motor carrier operating in California needs a CA number in addition to your USDOT number. A CA number is number designated to your business to access your business safety information, inspections et cetera. Your CA number must be displayed each side of your vehicle or truck being at least 2” inches in height. Commercial Vehicle Inspection specialists recommend that your CA, USDOT, & Regulation numbers be displayed in an easy to read font, and the color must contrast with the vehicle. When your truck numbers are easy to read, you make the commercial vehicle inspection specialists jobs a lot easier since they have to input all of your truck information in a system database.