Ark. Code Ann. § 23-13-256

It shall be unlawful for any common or contract carrier by motor vehicle to operate any vehicle upon the highways of this state unless there is painted, or otherwise firmly affixed, to the vehicle on both sides thereof, the name of the carrier and the certificate or permit number of the carrier. The characters composing the identification shall be of sufficient size to be clearly distinguishable at a distance of at least fifty feet (50') from the vehicle.