True or False: Reflex reflectors must be mounted at least 4 inches above the height of the rear tires on truck tractors.

Reflex reflectors must indeed be mounted at least 4 inches above the height of the rear tires on truck tractors. This requirement is designed to enhance visibility and safety by ensuring that reflectors can be seen by other motorists, particularly in low-light conditions. The positioning above the height of the rear tires helps to prevent the reflectors from being obscured by debris or other elements on the road, and it contributes to making the vehicle more noticeable from various angles. Hence, the statement is true.