Measurement of Retroreflection from Road Surfaces and Lane Markings 1999-01-1211
While driving his motor vehicle, the driver constantly looks at the lane marking to help with his or her coursing. The conspicuity of lane markings depends greatly on its retroreflection and that of the surrounding road surface area.
In this study, we measured in a darkroom the retroreflection performances of two types of pavement surfaces and also two types of lane marking, all of which are types currently in practical use. The following conclusions were reached as a result:
The reflection characteristics of lane marking
Compared to conventional type lane marking, high-luminance type lane marking exhibits a reflection characteristic that is approximately 3 and 5 times greater under dry and wet road conditions, respectively.
The reflection characteristics of road surfaces
From the initial time of paving, the luminance factor of a dense asphalt road surface rises roughly 5-to 6-folds with the passage of time. Thus, the whiteness of road surfaces increases with time.
The luminance factor of dense asphalt road surface that has been in use for a certain length of time drops to about a one-fourth level, when the road condition changes from dry to wet.
The contrast of luminance between road surface and lane marking
This contrast is far greater when (a) a high-luminance type lane marking and gas discharge headlamps are combined that when (b) a conventional type lane marking and halogen headlamps are coupled. The contrast is approximately 3 and 5 times greater under dry and weet road conditions, respectively, in favor of (a) over (b).