Rise-time requirements for high-intensity discharge headlamps. This research was sponsored by the University of Michigan Industry Affiliation Program for Human Factors in Transportation Safety.

This study had two objectives. The first, more general objective was to provide background information about the maximum rise time that should be allowed for high-intensity discharge headlamps. The second, more specific objective was to evaluate whether the current, rather stringent, Society of Automotive Engineers (SAE) recommendations should be relaxed or retained. To achieve these objectives, several scenarios were considered in which having early illumination is potentially of consequence. The scenarios included turning on the headlamps when starting to drive, turning on the headlamps when entering a dark tunnel, and switching between beams. New empirical data collected for this study included actual delays between turning on headlamps at night and starting to drive, and rise and falloff functions of tungsten-halogen low beams and high beams. It was concluded that rise-time requirements should be more stringent for systems with noncontinuous low beam than for systems with continuous low beam, as is the case in the current SAE recommendations. Furthermore, it was concluded that the current SAE recommendations for systems with noncontinuous low beam are justifiable. On the other hand, it was concluded that the SAE recommendations for systems with continuous low beams could be relaxed by eliminating all minimum light-output requirements for delays of less than one second.