Crash Reduction Effects of Flashing LED Stopsigns

摘要

A flashing LED stopsign is a regular octagonal stopsign with flashing light-emittingdiodes (LED) on its vertices. The hope is that by increasing the conspicuity of thestopsign the frequency of violations, and related intersection crashes, will be reduced. Atpresent however there does not appear to be conclusive evidence regarding the crashreduction effects of this treatment.In this paper, we implemented a hierarchical Bayesian approach to correct theregression-to-the-mean bias and estimate the right-angle crash reduction factor for thoseintersections installed flashing LED stopsigns in Minnesota. The treatment and referencegroup data were prepared based on Minnesota District Engineer and County Engineersurvey, Highway Safety Information System data, Minnesota Crash Mapping AnalysisTool data, and Google Maps observations. Three models with different predictors werefitted and five covariates were found to be significant, including the major road ADT, theminor road ADT, the major road speed limit, the minor road speed limit, and the numberof legs in the intersection.The point estimate of crash reduction factor indicates more than 40% reduction. Ithas a wide confidence interval due to the sample size of after treatment data and theprobability that it is greater than 0 is approximately 95%, suggesting that a decrease inthe frequency of right-angle crashes is associated with installation of flashing LEDstopsigns, but that the magnitude of this reduction remains uncertain. Once more after58treatment data are available in the future, the precision of crash reduction factor estimatecould be improved.