This chapter provides a general outline of road lighting, and does not attempt to provide a detailed coverage. The objectives of road lighting are to: (1) improve the safety of roads at night by providing good visibility conditions for all road users; (2) promote better traffic flow at night; and (3) enhance the amenities of the general area that is illuminated. Road fatalities and injuries at night can be reduced significantly if good lighting is installed in various critical sections of road. Road lighting terminology can be divided into photometric terms, relating to light and its measurement units, and lighting installation terms, which relate to physical equipment and its layout on the roadway. With road lighting, visibility of detail is relatively unimportant, but it is critical for road users to be able to discern clearly the presence and movement of any object on or near the road that may be a hazard; discernment may be by dark silhouette or reverse silhouette. It is also important to prevent glare from road lighting, which reduces road users' ability to see or causes them visual discomfort. The chapter also describes lamps, luminaires, luminaire mounting height, luminaire arrangements, luminaire overhang and bracket projection, and lighting column spacing and siting. For the covering abstract, see IRRD 892228.
Abstract