This document establishes performance, material, and design requirements and design guidelines for halogen replaceable light sources used in road illumination devices for forward lighting. Non-halogen filament light sources suitable for forward lighting are specified in SAE J573. The terms “high beam filament” and “low beam filament” used throughout this document refer only to typical use, not to a mandatory, exclusive, or universal function of the filaments. This SAE Recommended Practice is periodically updated to keep pace with experience and technical advances.