All vehicles transporting commercial medical waste shall be marked with letters or symbols four inches (4”) tall on a contrasting color background as "MEDICAL WASTE", "INFECTIOUS SUBSTANCE", "BIOMEDICAL WASTE", or the universal biohazard symbol as listed in 20 CAR § 53-304(c)(1) on the two (2) sides and back of the cargo carrying compartment, unless prohibited by the United States Department of Transportation.