Reduced lighting on freeways during periods of low traffic density

00457010137592491985Final reportArens, J.PDFTech ReportFHWA/RD-86/018;FCP 31P3-042DTFH61-83-C-00056Street lightingVisibilityBenefit cost analysisDriversFreewaysLegal factorsPersonnel performanceReduction (Chemistry)Traffic safetyRoads -- LightingRoads -- Safety measuresTraffic flowDriver performanceFreeway lightingLegal aspectReductionUnited StatesUnited States. Federal Highway AdministrationStaplin, L. K.Janoff, M. S. (Michael S.)Decina, L. E. (Larry E.)Ketron, Inc.United States. Federal Highway AdministrationFederal Highway AdministrationThe primary objective of this study was to determine if freeway lighting can be reduced or eliminated during nighttime periods when traffic volume is much lower than design capacity without causing significant reductions in the ability of drivers to control their vehicles in a safe and effective manner. This objective was met by the performance of ten tasks that included a review of the literature and state and foreign experiences; development of a conceptual model of visibility needs; identification of alternative light reduction tactics--including all (luminaires) off, every other off, one side off, and different types and levels of dimming; determination of the costs, potential energy savings, and potential legal implications of such light reduction tactics; and, finally, determination of the effect of such tactics on driver detection of simulated roadway hazards under actual traffic conditions. The major conclusions of this research are that present technology exists for implementing all of the identified tactics, with benefit-to-cost ratios greater than 1.0 for all but the most complex tactics; decrements in driver detection performance were measured under each reduced lighting tactic in comparison to performance under full lighting, minimally so for dimmed and every other configurations and significantly so for one sided and all off configurations; and, a potential for legal problems may result with the use of reduced lighting tactics. The recommendations arising from this research include the preferred use of fixed dimming circuits, primarily for new systems, with an inexpensive alternative being the extinguishment of every other luminaire for either new or existing systems