ABSTRACT
The presence of rain, snow, fog, dust, or smoke in the atmosphere makes the driver’s task more difficult, but in different ways. Rain has a direct effect on visibility by absorbing and scattering light and an indirect effect by changing the reflection properties of the road surface. Snow scatters incident light and in so doing creates a lot of visual noise in the driver’s visual field. In addition, if the snowfall is heavy enough, the snow will cover the road surface, obscuring lane markings and other information designed to aid the driver. Fog and heavy spray thrown up by other vehicles have their effect by absorbing and scattering light in the atmosphere, thereby reducing the luminance contrasts of everything ahead of the driver. Dust and smoke also absorb or scatter light and thereby reduce the effectiveness of all forms of lighting. It is the impacts of such adverse weather conditions on drivers and how lighting can be used to alleviate them that are the subjects of this chapter.
