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INTRODUCTION: Lighting for the outdoor environment is different than lighting an interior space. These differences present certain challenges not usually found in interior lighting. Outdoors, the universal standard is the daytime sun, yet night time electric lighting falls far short of daylight in numerous ways:

• Electric lights cannot light the sky as the sun does, therefore the night time "ceiling" is always dark, resulting in extreme contrasts compared with any light or lighted surface.

• No single man-made light source is as powerful as the sun, therefore numerous, smaller, close-by sources must be used. They can contribute to various forms of glare and thus impede "seeing" the surfaces of interest.

• At low light levels the eye works differently than at high light levels. Low light level receptors have highly specific requirements to detect, identify, and process the visual cues the brain needs to "see" and permit normal function.

• People encounter different emotions related to the night environment. Viewing dramatic scenery, sporting events, outdoor entertainment, and even feelings about personal security all have a personal impact that is largely controlled by lighting quality.

• Since the night scene provides minimal light boundaries, outdoor lighting can be "seen" at great distances. Night time visual clutter can be disturbing.

• Night time tasks, such as playing sports or driving automobiles, have very specific lighting requirements so people can perform these tasks safely and precisely.

• There is an expectation (or need) to control the light added to the outdoor environment. Some people want the dark for sleeping, star gazing, or privacy. When this need for darkness conflicts with other people's need for light, the control of light becomes critical, resulting in ordinances and bylaws.

This Recommended Practice will provide guidance in dealing with the preceding design considerations, allowing electric lighting systems to solve multiple needs while being responsive to the need for quality exterior lighting. There are a number of other Recommended Practices (RPs) that provide design guidelines for specific outdoor lighting applications. This document is not intended to supersede these other applicable RPs. Rather, it will link the various RPs together, augmenting them in subject areas not otherwise covered. It will also aid in the establishment of community themes and area classifications.