The primary purpose of roadway lighting is to provide a safe nighttime environment for vehicular and pedestrian traffic. For a lighting system to operate at maximum effectiveness, the lighting system maintenance should be considered and included during the system design process. Once a system has been designed and installed, proper maintenance then becomes essential to the reliability and continued high performance of the roadway lighting system. Like any lighting system, a roadway lighting system is subject to performance degradations. Exposure to the unfriendly outdoor environment makes timely system maintenance of paramount importance. If a roadway lighting system is not properly maintained, safety may be compromised in addition to the increased costs of deferred maintenance. The cost/benefit relationship of proper system maintenance should be determined by the individual owner based upon the needs for, and commitment to, system reliability. The purpose of this guide is to provide the designer and owner with an understanding of maintenance problems and procedures so that sound decisions can be made of maintenance practices that are appropriate for a roadway lighting system.