Nighttime visibility distances of various retroreflective stripes and raised pavement markers were determined in practice, on a dry and wet pavement and in the absence of public lighting. In addition, optical characteristics were measured in relation to the time lapse after application, in order to assess the effects of dirt and wear. Results were described in terms of coefficients of retroreflection, which were also used to predict visibility distances under other conditions than measured. Stripes with a verical profile and raised pavement markers both are better alternatives for nighttime visibility on wet roads than the more usual paint and thermoplastic markings. The raised pavement markers at first have a better visibility than the stripes, but are more sensitive to dirt and wear on a dry pavement. Dew appears to deteriorate the retroflection of the raised pavement markers by a factor of up to twenty; a smaller effect is found for the stripes.
Samenvatting