This SAE Recommended Practice provides test procedures, requirements, and guidelines for high-mounted stop lamps intended for use on vehicles 2032 mm or more in overall width. This document applies to trucks, motor coaches, van type trailers, and other vehicles with permanent structure greater than 2.8 m high. This document does not apply to school buses, truck tractors, pole trailers, flat-bed trailers, and trailer converter dollies. The purpose of the high-mounted stop lamp or lamps is to provide a signal over intervening vehicles to the driver of following vehicles.
The SAE Heavy Duty Lighting Committee decided that a standard was needed for high-mounted turn signal lamps for the rear of large vehicles. Since most vehicles use the same or very similar lamp(s) for stop lamps and turn signal lamps it was decided to use the high-mounted stop lamp as the basis for the high-mounted turn signal lamp. Therefore high-mounted turn signal lamps were included in SAE J1432.