Reflectance measurements on three pavement surfaces using CMH and HPS lamps

The comparative reflective properties of relevant road surfacing materials under conventional high pressure sodium (HPS) and prototype ceramic metal halide (CMH) lighting were assessed. The expected luminance distribution and small target visibility distribution were calculated for the full-scale street lighting trial carried out at TRL, UK and for the pilot study in Albi, France. The samples tested were taken from the site of the road trial at TRL and one of the roads in the trial at Albi. A sample of negatively textured thin surfacing was also included. A total of 308 measurements were made on the samples. The data showed that the CMH lamp spectrum, but not the HPS lamp spectrum, changed with orientation of the lamp axis with respect to the vertical. More of the light from the CMH lamp was measured in the shorter wavelengths when the lamp axis was vertical. The measurements demonstrated that this effect was responsible for the changes in spectrum seen in this experiment.