Driver Perception of Just Noticeable Differences of Automotive Signal LampIntensities

摘要

The National Highway Traffic Safety Administration (NHTSA) often receivespetitions for determination of inconsequential non-compliance from manufacturers regarding vehicle lamp intensities which fall just outside the performance limits as specified in Federal Motor Vehicle Safety Standard 108. They assert that most drivers could not notice the difference, and thus the non-compliance is inconsequential. Typically, a non-compliance regarding intensity has been deemed inconsequential to safety when the performance has been less than 25% above or below the boundary limit. This study empirically evaluated the just-noticeable difference (JND) of several signal lamp types under typical ambient illumination and viewing distance conditions to provide an objective basis for assessing waiver requests. The procedure involved a paired comparison of standard light sources filtered to simulate color and intensity differences. Based on the findings, a difference of up to 25% from FMVSSS 108 intensity requirements appears to be a reasonable criterion for use in decisions regarding the inconsequentiality of non-compliant signal lamps.