Evaluation of Photometric Data Files for Use in Headlamp Light Distribution

Computer simulation of nighttime lighting in urban environments can be complex due to the myriad of light sources present (e.g., street lamps, building lights, signage, and vehicle headlamps). In these areas, vehicle headlamps can make a significant contribution to the lighting environment ^{1 , 2} . This contribution may need to be incorporated into a lighting simulation to accurately calculate overall light levels and to represent how the light affects the experience and quality of the environment. Within a lighting simulation, photometric files, such as the photometric standard light data file format, are often used to simulate light sources such as street lamps and exterior building lights in nighttime environments. This paper examines the validity of using these same photometric file types for the simulation of vehicle headlamps by comparing the light distribution from actual vehicle headlamps to photometric files of these same headlamps. Light values are calculated in a simulated environment and numerically compared to light measurements taken in situ of actual headlamps. A discussion of how light distribution of a photometric file differs from light distributed by an actual headlamp assembly is included to articulate the primary differences.