Costs, benefits, and legal implications of reduced freeway lighting

A group of lighting experts were asked to rate various reduced lighting systems with respect to potential effects on energy use, safety, other traffic operations, practicality, cost, and legal problems. Both older, oil-embargo related systems, such as turning off the lights on all or part of specified roadways during various time periods, and modern systems controlled by special ballasts, electronic sensors and controls, and computers were studied. The simplest (all off) tactic and dimming 50 percent after midnight scored highest, followed by two luminaires per pole, one side of, variable level lighting as a function of traffic volume, and every other light out after midnight. The simplest systems had very high benefit/cost ratios, while the more sophisticated systems scored higher in safety results and legal implications. A review of court cases and the legal literature indicate that municipal agencies would be liable for damages incurred as a result of reduced lighting. It is therefore imperative that the decision to reduce lighting be based on sound scientific information encompassing every foreseeable contingency.