Reflectors required by § 22-208 of this subtitle shall be mounted at a height of not more than 60 inches nor less than 15 inches above the ground on which the vehicle stands. However, if the highest part of the permanent structure of the vehicle is less than 15 inches, the reflector at that point shall be mounted as high as that part of the permanent structure will permit. The rear reflectors on a pole trailer may be mounted on each side of the bolster or load. Any required red reflector on the rear of a vehicle may be incorporated with the tail lamp, but the reflector shall meet all the other reflector requirements of this title. Clearance lamps shall be mounted so as to indicate the extreme width of the motor vehicle, not including mirrors, and as near the top of the vehicle as practicable. When rear identification lamps are mounted at the extreme height of the vehicle, rear clearance lamps may be mounted at an optional height. When mounting of front clearance lamps at the highest point of a trailer results in those lamps failing to mark the extreme width of the trailer, they may be mounted at an optional height, but must indicate the extreme width of the trailer. Clearance lamps on truck tractors shall be so located as to indicate the extreme width of the truck tractor cab. Clearance lamps and side marker lamps may be mounted in combination if illumination is given as required in this subtitle with reference to both. However, no clearance lamp may be combined with any tail lamp or identification lamp.