PART 2
ROADWAY LIGHTING
Formerly, State Electrical Engineer
Alabama Department of Transportation
Montgomery, Alabama
Manager, Electrical Department
Volkert & Associates
Mobile, Alabama
Brian L. Bowman, Ph. D., P. E.
Professor of Civil Engineering
Auburn University
Auburn, Alabama
Part 2 of this chapter presents considerations in the selection of lighting for freeways and other types of roadways. Both standard and high mast lighting are addressed. Roadside safety and the application of various types of bases are discussed and illustrated. Information on construction, acceptance testing, and maintenance is presented. An extensive list of references, which are noted in the text, concludes the section. Portions of this material were derived from studies made under a Federal Highway Administration Project, “Design, Construction and Maintenance of Highway Safety Features and Appurtenances.”
714 BENEFITS AND FUNDAMENTALS OF LIGHTING
Properly designed and installed roadway lighting can result in significant reductions in
nighttime traffic accidents, act as a deterrent to crime, increase commercial activity,
and improve aesthetic value. Roadway lighting increases traffic safety by enhancing the visibility of potential roadway hazards, other vehicles, pedestrians, and roadway geometrics. Pedestrians are among the largest beneficiaries of lighting installed on urban streets. Studies indicate reductions of up to 80 percent in pedestrian accidents and reductions ranging from 20 to 40 percent for all types of night accidents [1]. Another study identified a 40 percent reduction in the ratio of night accidents to day accidents resulting from the installation of roadway lighting on freeways [2]. While these figures are significant, it is anticipated that the safety benefits derived from the installation of roadway lighting will become even more pronounced in the future. This is due to the increasing age of the driving population and the significantly reduced visual abilities of persons over 65 years of age. The savings realized by accident prevention alone can often justify the costs of a modern lighting system [3].
Although much progress has been made in improving lighting system efficiency and effectiveness, there are still many streets, particularly in small communities, that are not lighted in accordance with present guidelines. This is primarily due to the scarcity of local funds, which can be mitigated by the use of federal funds on qualifying projects. Roadway lighting has been recognized as a viable countermeasure for increasing traffic safety since 1966, when federal legislation enabled federal aid expenditures for construction and maintenance of roadway lighting [4].
The benefits of providing roadway lighting include enhancing traffic safety, improving pedestrian visibility, deterring crime, improving commercial interests, and promoting community pride. The actual benefits obtained are dependent upon the type of facility and area in which the lighting will be installed. Only the traffic operational and safety benefits obtained from the proper design and installation of roadway lighting are discussed in this chapter. It should be noted that properly designed and installed roadway lighting can result in roadway facilities operating almost as efficiently and safely at night as during the daytime. Lighting cannot, however, be expected to achieve the same safety levels as daytime operation, because of the influence of other factors, such as fatigue, higher speeds, and intoxication, which make a greater contribution to nighttime accident frequency.
