EVALUATION OF HEADLAMP SYSTEMS FOR NIGHTTIME SAFETY: THEIR RELATIONSHIP TO RETROREFLECTIVE TRAFFIC SIGN PERFORMANCE

Decisions regarding low-beam headlamp modeling are generally made following evaluation of pedestrian target visibility and glare to oncoming motorists. Retroreflective traffic control signs are parts of the model that have long been ignored, yet they are essential adjuncts to safety. The widespread use of retroreflective materials for information, regulation, and warning signs and their inclusion in many official standards suggested that the comparison of U.S. and Economic Commission for Europe (ECE) lower-beam headlamps should be made to reveal the 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 was used to determine the luminances for three types of material. The study permits comparisons among existing headlamp types and illustrates the significant deterioration in sign luminances that accompanies the use of ECE lower beam headlamps, or the alteration of U.S. lower beam photometrics to more closely correspond to those of ECE headlamps. The study permits some consideration of retroreflective material choice, depending on headlamp type, sign position, and sign luminance requirements.