Retro-reflectivity is the ability of a road marking to reflect light from a vehicle’s headlights back to the driving position of a vehicle. Initially it will be determined by the amount of glass beads spread on the line. The continuing performance of the line is determined by the amount and quality of glass beads included in the body of the road marking. Retro-reflectivity is measured using a piece of equipment known as a Reflectometer. For reflection in daylight or under road lighting the luminance coefficient in diffuse illumination Qd is used and is expressed in mcd/m2/lux. Retro-reflectivity is measured using a Reflectometer.
Luminance is the property of the marking which describes the brightness of its colour. Luminance poses difficulties of compliance where the Texture Depth of the road surface is above 2mm. Where the surface is very coarse; eg. newly surface dressed roads with a texture depth of 4.5 mm it may prove extremely difficulty to achieve a luminance value, hence Class B0 may have to be specified. Luminance is measure using a Luminance metre.
Chromaticity is the definition of the colour of the line by reference to the CIE chromaticity diagram. Chromaticity is measured also measured using a Luminance metre.
Skid resistance measurement on road markings is carried out using the standard British pendulum apparatus. The units of measurement quoted in IS EN 1436 are followed by the abbreviation SRT. IS EN 1436 has a range of Skid Resistance Classes ranging from S0 to S5. The Skid Resistance Class specified for white and yellow road markings on public roads in Ireland should be Class S2 SRT > 50. The skid resistance of freshly applied road markings tends to increase in value due to the effects of trafficking and weathering. For items such as transverse yellow bar markings at roundabouts, hatching and chevron areas, a higher Class of skid resistance is generally specified.
A Guide to the European Standard for Road Markings IS EN 1436