This SAE Recommended Practice applies to functions of motor vehicle signalling and marking lighting devices which use light emitting diodes (L.E.D.'s) as light sources. This report provides test methods, requirements, and guidelines applicable to the special characteristics of L.E.D. lighting devices. These are in addition to those required for devices designed with incandescent light sources. This report is intended to be a guide to standard practice and is subject to change to reflect additional experience and technical advances.