R.I. Gen. Laws § 31-23-27
No person shall operate or cause to be operated any bus, truck, full trailer or semi-trailer, of registered gross weight exceeding three (3) tons, on any public highway in this state unless it is equipped with suitable metal protectors or substantial flexible flaps behind the rearmost wheels. In case the rear wheels are not covered at the top and rear by fender, body, or other parts of the vehicle, the rear wheels shall be covered at the top and rear by protective means of a standard type or design and so installed as to reduce, as far as practicable, the wheels from throwing dirt, water, or other materials on the windshields of following vehicles, except in cases in which the motor vehicle is so designed and constructed that the requirements of this section are accomplished by reason of the fender or body construction or other means of enclosure. However, §§ 31-23-26 - 31-23-28 shall not apply to vehicles where their construction is such that complete freedom around the wheel area is necessary to secure the designed use of the vehicle. Violations of this section are subject to fines enumerated in § 31-41.1-4.
R.I. Gen. Laws § 31-23-27