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Bullough, J. D., Donnell, E. T., & Rea, M. S. (2013). To illuminate or not to illuminate: roadway lighting as it affects traffic safety at intersections. Accid Anal Prev, 53, 65–77.
Abstract: A two-pronged effort to quantify the impact of lighting on traffic safety is presented. In the statistical approach, the effects of lighting on crash frequency for different intersection types in Minnesota were assessed using count regression models. The models included many geometric and traffic control variables to estimate the association between lighting and nighttime and daytime crashes and the resulting night-to-day crash ratios. Overall, the presence of roadway intersection lighting was found to be associated with an approximately 12% lower night-to-day crash ratio than unlighted intersections. In the parallel analytical approach, visual performance analyses based on roadway intersection lighting practices in Minnesota were made for the same intersection types investigated in the statistical approach. The results of both approaches were convergent, suggesting that visual performance improvements from roadway lighting could serve as input for predicting improvements in crash frequency. A provisional transfer function allows transportation engineers to evaluate alternative lighting systems in the design phase so selections based on expected benefits and costs can be made.
Keywords: Lighting; Accident Prevention/*methods; Accidents, Traffic/*prevention & control/psychology/statistics & numerical data; Cross-Sectional Studies; *Environment Design; Humans; *Lighting; Minnesota; Models, Statistical; Photoperiod; Psychomotor Performance; Regression Analysis; Safety/statistics & numerical data; Visual Perception
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Monsere, C. M., & Fischer, E. L. (2008). Safety effects of reducing freeway illumination for energy conservation. Accid Anal Prev, 40(5), 1773–1780.
Abstract: The addition of illumination where none was present is generally believed to have a positive effect on motor vehicle safety; reducing the frequency, as well as the severity of crashes. The operational cost of illumination, however, can make it a candidate for conservation during periods of high energy costs. In response to a forecasted energy shortage, the Oregon Department of Transportation selectively reduced illumination on interstate highways as part of an energy-saving effort. The reductions occurred at 44 interchanges and along 5.5 miles of interstate highway. This paper presents the results of a crash-based analysis of the changes in safety performance using an empirical-Bayes observational methodology. The study found an increase in reported crashes where the lineal lighting was reduced both in total crashes (28.95%, P=0.05) and injury night crashes (39.21%, P=0.07). Where full interchange lighting was reduced to partial lighting, a 2.46% increase (P=0.007) in total night crashes was observed. Injury night crashes, however, decreased by 12.16% (P<0.001) though day injury crashes also decreased at these locations. Unexpectedly, for interchanges where illumination was reduced from partial plus to partial, a 35.24% decrease (P<0.001) in total crashes and 39.98 (P<0.001) decrease in injury night crashes was found, though again, day crashes also decreased.
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