Measurement of the daytime visibility of road markings

Areas of Expertise (1)

Measurement of the daytime visibility of road markings with BRRC’s Qd30 instrument

The result of this measurement, daytime visibility, is the luminous intensity from a surface unit of sampled road marking, as perceived by a motorist from a distance of 30 m; it is expressed per unit of illumination of the marking under diffuse lighting conditions. Diffuse lighting can be compared to natural lighting under a clouded sky, or street lighting at night. Daytime visibility is expressed in mcd lx-1m-2. Typical values for the daytime visibility of new white markings range between 100 and 200 mcd lx-1m-2. On concrete, which is lighter in colour, usually a higher initial value is required than on asphalt, since not only absolute daytime visibility is important, but also the contrast of the marking with the surrounding road surface. The measuring apparatus available at BRRC is a Qd30 instrument of the DELTA company; it is described in more detail in BRRC’s information leaflet F56.