MEASURING WET-NIGHT DELINEATION REFLECTIVITY

Reflectorized pavement markings provide drivers valuable continuous information about the roadway and its characteristics. In particular, edge lines provide a strong orientational influence, whereas centerlines indicate the direction of traffic and further delineate the traveling lane. Unfortunately, pavement markings can lose their reflectivity, and thus their visibility, on dark rainy nights just when drivers are more apt to actively look to them for guidance. Much research has been devoted to the issue of wet-night visibility. Available methods of measurement have been limited to panels of visual evaluators and telephotometers. Both methods are difficult to apply in field test programs. This paper focuses on the problems involved in measuring wet performance easily and effectively and discusses an alternative measuring system. A new concept in retroreflectometers currently being researched uses a laser light source and a narrow band-pass filter to block ambient light. This mobile, day/night, wet/dry instrument should help accelerate development and demonstration of wet reflective delineation and provide insights and better understanding of the relationship between delineation performance and drivers' visual needs.