Evaluation of headlamp systems for night–time safety

Decisions about the modelling of low–beam headlamps are generally made following evaluation of pedestrian target visibility and glare to oncoming motorists. Retroreflective traffic control signs are a part of the model which have long been ignored, yet they are an essential adjunct to safety. The widespread use of retroreflective materials for information, regulation and warning signs and their inclusion in many official standards suggested to the authors that the comparison of US and ECE lower beams would reveal the serious consequences of further light reduction above the horizontal axis. Comparison of photometrics above the horizontal axis in the direction of commonly placed traffic signs for a variety of distances were used to determine the luminances for three types of material. The study permits comparisons between existing headlamp types and illustrates the significant deterioration in sign luminances which accompanies the use of European lower beams, or the alteration of US lower beam photometrics to more closely correspond to European lamps. The study permits some consideration of retroreflective material choice, depending on headlamp type, sign position, and sign luminance requirements.