CANCELLED JANUARY 1996 This document provides design parameters, performance requirements, and general installation recommendations for supplemental high mounted stop and/or rear turn signal lamps, intended to supplement stop and/or rear turn signal lamps described in SAE J586 and SAE J588, for use on vehicles less than 2032 mm in overall width. Lamps for vehicles more than 2032 mm in width are covered in SAE J1432.

Reason for cancellation: J1957 provides requirements for CHMSLS for vehicles less 2032 mm overall width. J186a is referenced in FMVSS 108.