Evaluation of Light Reflectiveness of Modern Pavement: Standard Tungsten Incandescent and LED

Abstract

The objective of this research was to evaluate the reflectiveness of the two most commonly used modern pavement systems in the United States (concrete and asphalt). The R table used for roadway lighting design were established several decades ago as a critical parameter for determining the light reflectivity (luminance) of pavement surfaces. With the existence of modern pavement systems and also the new lighting technologies, it is necessary to examine the applicability and representability of the current R table. A total of 12 different pavement surfaces were evaluated to characterize the light reflectivity of two light sources [incandescent and light-emitting diodes (LEDs)]. The reflective properties of the pavements were evaluated considering the influence of angular light (incident lighting angles), defined as observation angle (α), rotation angle (β), and incident angle (γ). The testing program evaluated five incident angles, (0°, 27°, 45°, 63°, and 79°) between the observation plane and the incident light plane (γ). These five angular measurements were repeated with the combination of four rotation angles (0°, 15°, 30°, and 45°) measured between the incidence light plane and the observation plane (β). A total of 1,200 luminance measurements were performed on 12 pavements, four cast or cored pavement samples together with eight in situ field-tested pavements. Light intensity (illuminance) and pavement reflectivity (luminance) were measured. A customized portable goniometer was used to measure the light reflectivity of various pavements. Research results showed that there is statistical difference in light reflectiveness of concrete and asphalt with respect to different light sources. In addition, the angular light distribution significantly differs between standard (incandescent) and LED lights. In addition, the proposed testing method cannot only efficiently evaluate light reflectiveness in the field but also captures light reflectiveness of surface conditions exposed to various light sources.