Improving the Visibility of Road Markings

Recent collaborative European research has established that the minimum distance at which road markings should be visible to drivers must be equivalent to two seconds of travel time5. Several factors decide the distance at which a road marking is visible.4,5Most of them are related to the driver, for example, the driver’s vision, headlight strength, car cleanliness, or are unavoidable, for example, rain or glare from oncoming vehicles. However, the composition of the road marking can be designed to optimize its visibility in a variety of conditions. For instance, the bright color of road markings is maintained by using titanium dioxide pigment, and the accumulation of dirt on markings can be prevented by adding crystallized titanium dioxide. Such accumulation of dirt on markings is likely to reduce their visibility.

The majority of the light emitted by the headlights, which hit the surface of the road, is either reflected forwards or absorbed by the road surface itself with just a fraction of the light reflected back towards the driver's eyes. Retroreflection is referred to as the reflecting of light back in the direction of the light source.5,6 As the coefficient of retroreflected luminance increases, the contrast between the road surface and the road marking also increases. When the light from the headlights which a road marking reflects back to the driver is more, the visibility of the road marking will also be more, particularly in bad weather and at night.