Sensitivity Analysis of Headlamp Parameters Affecting Visibility and Glare December

Traffic Safety Administration, in the interest of information exchange. The opinions, findings and conclusions expressed in this publication are those of the author(s) and not necessarily those of the Department of Transportation or the National Highway Traffic Safety Administration. The United States Government assumes no liability for its content or use thereof. If trade or manufacturers' names or products are mentioned, it is because they are considered essential to the object of the publication and should not be construed as an endorsement. The United States Government does not endorse products or manufacturers. Computer-simulated evaluations were conducted to identify the extent to which driver visibility and glare are affected by headlamp light source type (e.g., tungsten-halogen or high-intensity discharge), mounting height, optical system type, alignment type, and mis-aim. Based on the results of these simulation evaluations, this study also addressed whether further limits might be considered in photometric standards for headlamps that are addressed by Federal regulations. While there appears to be an inherent conflict between visibility and glare in the photometric design of headlamps, the analyses performed here do indicate that current photometric specifications for headlamps do not always trade off visibility and glare equally (e.g., headlamps that provide equivalent forward visibility as characterized here can result in different levels of disability or discomfort glare). The findings imply that advanced (dynamic) forward-lighting systems (AFS), if they can be made practical, might be of benefit in adjusting headlamp luminous intensity distributions in various situations to maximize visibility while controlling glare within acceptable limits. 17. Executive Summary As discussed in a recent report on nighttime headlamp glare from the National Highway Traffic Safety Administration (NHTSA) to the U.S. Congress, a number of factors can contribute to the extent to which drivers experience reduced visibility and discomfort from oncoming vehicle headlamps. These include the lamp type (e.g., tungsten-halogen or high-intensity discharge [HID]), lamp mounting height, headlamp optical system type (e.g., whether headlamps use reflector or projector systems), and the alignment of lamps. Computer-simulated evaluations were conducted to identify the extent to which driver visibility and glare are affected by these factors. The degree of conformity of headlamps to current U.S. photometric regulations (both minimum and maximum intensity) for headlamps (Federal Motor Vehicle Safety Standard [FMVSS] 108) was also evaluated. The evaluations used photometric data for 12 headlamps available in the United States, covering a sample including several headlamps with different characteristics as described …