NEW IMAGE BASED MEASUREMENT METHOD OF REFLECTIVE PROPERTIES OF ROAD SURFACES (OP39, 284-293)

Designing a road lighting installation without the knowledge of the reflective properties of the road surface can lead to incorrect luminance levels and distributions, which in turn may cause lower safety and/or energy efficiency. The standard measurement method to determine the reflective properties of road surfaces, the r-tables, is not required by standards and rarely used. Other, non-destructive in situ measurement methods have not been asserted themselves. Cheap, easy and non-destructive methods are desired. Hence, the authors are investigating a method where luminance image processing is used to calculate reflective properties of street lighting scenes. With the help of a calibrated additional luminaire and several luminance images the reduced luminance coefficients in all relevant points of the measurement field are calculated and interpolated to the standard r-table format. With them, simulations in Radiance are made and compared to other simulations where precise measured r-tables and measurements were available.