United States Department of Transportation
i
Safety Evaluation of Red Light Running Camera Intersections in Illinois
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2017-04-01
[PDF-2.32 MB]
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Edition:Final Report, August 16, 2016 - April 15, 2017
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Abstract:As a part of this research, the safety performance of red light running (RLR) camera systems was evaluated for a sample of 41 intersections and 60 RLR camera approaches located on state routes under IDOT’s jurisdiction in the Chicago suburbs. Comprehensive traffic crash analyses based on 3 years of before-installation crash data and 3 years of after-installation crash data were conducted in order to evaluate the safety effects of the RLR cameras. Two methods were used to evaluate the crash experience at the RLR camera locations: the naive before and after, and the empirical Bayes. The observed crash reductions were tested for statistical significance using the Poisson test at a 95% level of confidence. Using the empirical Bayes method for those crash types where safety performance factors (SPFs) were available, crash modification factors were developed for statistically significant crash reductions based on the unbiased index of effectiveness metric. The results of the naïve before and after and the empirical Bayes methods indicated statistically significant reductions in total intersection crashes of 36% to 34% and in angle RLR intersection crashes of 53% to 67%, respectively. Other findings of the installation of the RLR camera system based on the naïve before and after method indicated significant reductions in intersection injury crashes of 18% and a non-significant change in rear-end RLR crashes. The resulting crash modification factors are 0.656 for total intersection crashes and 0.331 for angle RLR intersection crashes. Overall, the safety evaluation provides evidence that the installation of RLR camera systems on state routes reduces angle RLR crashes, which are associated with severe injury; has a nominal impact on rear-end RLR crashes; and has a positive impact on reducing total intersection crashes, as studied in Chicago suburbs. It is recommended that IDOT continue to support the installation of RLR cameras at locations where justified, thereby improving intersection safety for Illinois motorists.
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