Investigating the Accuracy of Road Surface Reflection Characterisation Based on Round-Robin Measurements

Knowing the reflection properties of road surfaces is necessary for road lighting design. Road surface reflection is commonly specified by a set of luminance coefficients q. However, measured data q are limited and a fortiori, little is systematically known about the accuracy of measurements. To address this, a comparison based on the recommendations of standard ISO 5725 was organized among three laboratories. Seven samples were measured (six different road surfaces and one near diffuse reflective material). The calculations include trueness and precision. While trueness was checked for a suitable geometry (as we lack reference road surface reflection data) and was found to be quite good, the precision proved to be quite variable, e.g. for characteristic values versus those of single q-values. Precision was not closely related to the values of q, but rather to the geometrical conditions of the measurement.