scope:

Purpose of this Standard Practice

The primary purpose of this Standard Practice is to serve as the basis for design of fixed lighting for roadways, streets, adjacent bikeways, and pedestrian ways. The Standard Practice deals entirely with lighting design and does not give advice on construction. Its primary purpose is to provide recommended practices for designing new continuous lighting systems for roadways and streets. It is not intended to be applied to existing lighting systems until such systems are completely redesigned. It has been prepared to advance the art, science, and practice of roadway and street lighting in North America. Roadway and street lighting includes pedestrian and bikeway lighting when it is associated with the public right-of-way.

In those circumstances where there is any doubt as to whether the provision of new or updated roadway lighting would provide a benefit at a particular location, a decision should be made based on a study of local conditions. Once a decision has been made to provide lighting, this publication provides the basis for designing an appropriate system. The AASHTO Lighting Design Guide provides guidance for warranting.

Purpose of Roadway and Street Lighting

The principal purpose of roadway and street lighting is to allow accurate and comfortable visibility at night of possible hazards in sufficient time to allow appropriate action. For a pedestrian, this can mean better visibility of the surrounds and the sidewalk, while for the driver of a motor vehicle, it will mean time to stop or to maneuver around an obstacle. Good lighting has been shown to significantly reduce the night proportion of accidents; especially on urban freeways and on major streets. For most streets and sidewalks, good lighting has been reported to increase the feeling of personal security of pedestrians.

The benefits of lighting should be considered against the drawbacks; engineering, capital and maintenance costs, energy use, appearance--particularly of overhead wires, but sometimes also of poles--the added fixed object hazard of poles, plus spill light on adjacent residential or commercial (i.e., outdoor dining) property and into the sky (affecting astronomical observations). Thus, lighting is 'good' when it is economical in equipment, energy and maintenance costs, and meets a proven or reasonably predictable need, with a minimum of adverse effect. This Practice has been developed to provide guidance to experienced engineers in designing such lighting.