METHODOLOGY FOR DETERMINING PAVEMENT REFLECTIVITY FOR ROADWAY LUMINANCE CALCULATION

The field test procedures for determining the reflective properties and the macrostructure of a pavement surface are described. The light-reflecting characteristics of roadway surfaces affect the quantity and quality of light reflected (luminance) from the pavement. The luminance of the pavement surface and its uniformity affect the visibility of objects on the roadway surface. The uniformity of luminance patterns reduces confusion and clutter and stabilizes the driver's adaptation state. Improved visibility through better roadway lighting can result in increased safety for the nighttime driver. The luminance of the pavement is the product of the light arriving at a point (illumination) multiplied by the luminance factor. The luminance factor represents the directional reflectivity of the pavement, which is a function of light source location, observer location, and macrostructure or microstructure of the pavement. The parameters used for test-site selection and a matrix of test-site variables are presented. Once a test site has been selected, the test-site locations for reflectance measurements, British portable tester, and sand patch are defined, and the preparation and measurement techniques are described. As reported in the paper, problems were discovered in the reflectometer mechanism electronics that invalidated the test data. The methodology presented provides insight into the complexities of making pavement reflectance measurements. The procedures described lay the foundation for subsequent field measurements. The measurements are required to establish a simplified pavement reflectance classification system that is crucial to roadway luminance calculations.