Misdirected or misapplied outdoor lighting is a concern for aesthetic, environmental and energy management reasons. Roadway lighting has been estimated to account for approximately 30 percent of sky glow and light trespass. While the concerns and solutions for stray light problems associated with roadway lighting can be described in several different ways, this Technical Memorandum addresses three components: sky glow, light trespass, and glare. It then suggests lighting design solutions, which can be used as the basis for lighting ordinances or regulations.

Following some brief introductory statements, this Technical Memorandum contains four major sections: stray light defining the major components (sky glow, light trespass, and glare) and giving some historical perspective on related problems/concerns; community ordinances and regulations providing the rationale for creating uniform ordinances based on scientific principles rather than political pressure; methods for measuring and evaluating stray light summarizing methods advocated by the Commission Internationale de lEclairage (CIE) and describing a simple non-technical method for measuring light trespass using a light meter from the Light Trespass Research Report published in March, 2000; and solutions and mitigation giving alternative approaches for dealing with existing sky glow and light trespass problems through prevention and remedial modification.

The impact of roadway lighting upon animal or plant life is outside the scope of this Technical Memorandum, but should not be ignored by designers and engineers responsible for outdoor lighting.