Official Title: Safety Evaluation of Red-Light Cameras
Authors: Forrest M. Council, BMI-SG; Bhagwant Persaud, Ryerson University; Kimberly Eccles, BMI-SG; Craig Lyon, Ryerson University; and Michael S. Griffith, Federal Highway Administration.
This is a 2005 study by the Federal Highway Administration(FHWA) on the effects of red-light cameras in 132 intersections across seven municipalities in the USA. This study compares the before and after crash statistics of those RLC intersections using the Bayesian statistical analysis method as well as calculating the estimated economic impact of the presence of RLCs at intersections. The crash statistics used in this study use various distances from 20 to 158 feet as their Distance-From-Intersection inclusion zone for crashes. The study uses from 48 to 108 months of pre-RLC crash data compared to 10 to 60 months of post-RLC data. The statistics used in this analysis are from various state, city and county authorities. The study focuses on the total cost of crashes, not the percent of change in crashes like most of the other studies on the subject do, and in fact no total crash percentage statistics are listed in the summary or conclusions anywhere. Pulling from their total rear-end and right-angle crash statistics, there was a 1% decrease in total crashes across this study at RLC-enabled intersections. Data collected from this study was released in a 2011 USF report that showed a 10% increase in fatalities over the course of this 2005 FHWA study, although it is not specifically cited in the study itself . The final conclusion reached by the study is: "RLC systems do indeed provide a modest aggregate crash-cost benefit... The indications of a spillover effect point to a need for a more definitive study of this issue".
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This is a detailed 98 page study, that uses data collected in differing ways using differing specifications by different jurisdictional entities at various state, county and city levels. There are several mentions of inconsistencies in the data collected, but this is really the largest and most comprehensive multi-state study on the subject that has been released in spite of it's flaws. All of the data used in this study at this point is at least 9 years old, including the economic impact figures that are based on 2001 numbers which have undoubtedly changed in the last 10 years. In spite of the fact that they had stated that this study would be updated it has not been updated in the last 6 years. The lack of any meaningful crash data per jurisdiction being shown, as well as the fact that the municipalities were guaranteed anonymity in the limited reporting of crash data that is shown means that the data is not verifiable. Since fatalities were excluded from the crash costs in this study, and the fatalities increased during the study period, if those fatalities are included in the calculations the crash costs are shown to increase after RLCs were installed. The conclusions are supported by the limited and unverifiable data that is shown.
This study has a thorough analysis of other previously released studies on the issue of RLC safety issues, and concludes that "most studies are tainted by methodological difficulties that raise questions about any conclusions from them". Specifically the Oxnard, CA study is criticized for its failure to "separate the specific effects at treatment sites from citywide effects".