Delaware DOT, DE, USA 2007 RLC Study

Official Title: Electronic Red Light Safety Program, After Analyses Summary

Authors: Carolann Wicks, Secretary

Summary:
This is a 2007 study by the Delaware Department of Transportation on the effects of red-light cameras in the state of Delaware. This study compares the before and after crash statistics of 20 RLC intersections in that state. The study uses 36 months of pre-RLC crash data compared to 9 to 12 months of post-RLC data. The statistics used in this analysis are from the Delaware Department of Transportation which does not define what they use as their Distance-From-Intersection inclusion zone for crashes. There are no data or conclusions in this report that suggest a reduction or increase in fatalities due to RLCs. This report does not cover injury crashes. The results show that "total intersection crashes decreased, or improved, at 16 of the 20 intersections" over the study period, an overall percentage change is not given. The study concludes that: "The ERLSP(Electronic Red Light Safety Program) has largely been successful."

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Comments:
This is a detailed 63 page study, the data and statistical analysis appear inconsistent and selectively chosen, and the raw true total crash data is not shown in the study except in bar-chart form. The selection of 20 RLC intersections is slightly above-average number of intersections for this kind of study. The lack of a defined Distance-From-Intersection inclusion zone for crashes somewhat lowers the value of the statistics. The before and after RLC date periods are not sequential and the post-RLC periods are mostly less than 12 months due to the exclusion of the first 3 months of RLC data "to allow drivers to be acclimated to the presence of red light enforcement equipment", (which is a reason that we have not seen before in other related studies with the exception of the 2002 Oxnard, CA study which only skipped 2 months). This removes up to 25% of the post-RLC data from some of these intersections, decreases the consistency of the data and decreases the validity of any statistical analysis done with this data. Another anomaly is the choice to calculate "Total crashes" as all crash types in some datasets and "angle and rear-end" type crashes only in other datasets, leading to inconsistent analysis and further degrading the results of the study. There are no control intersections used to validate the findings of this study, further degrading the results given. The costs and revenues of the program show that in the most recent year of operation the program(2006) lost money for the state. The conclusions of this study are somewhat supported by the limited selective data supplied.

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St Pete Driver,
Dec 23, 2012, 5:38 AM
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