Official Title: Reductions in Injury Crashes Associated With Red Light Camera Enforcement in Oxnard, California
Authors: Richard A. Retting, MS, and Sergey Y. Kyrychenko, MS
This is a 2002 study on red-light cameras in the City of Oxnard, California that compares the before and after crash statistics where there are 11 RLC intersections in that city. The analysis uses at least 29 months of pre-RLC crash data compared to 29 months of post-RLC data. The statistics used in this analysis are from the California Statewide Integrated Traffic Records System (SWITRS) and the Distance-From-Intersection inclusion zone for crashes is not specified. There are no data or conclusions in this report that suggest a reduction or increase in fatalities due to RLCs. The data shows that crashes city-wide decreased 5.4% during the study period after RLCs were installed. Controls for this study are created by using whole-city crash data at three other California cities that are over 100 miles from Oxnard and are considered similar in size to Oxnard. The conclusion arrived upon is: "We estimated that red light camera enforcement would reduce the number of crashes at signalized intersections in Oxnard by 7%".
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This is a brief 4 page study summary, but the data appears to be valid, the selection of 11 RLC intersections is slightly below average for this kind of study. There is significant pre and post-RLC data, but removing the crash data from the first two months of RLCs being enabled decreases the consistency of the data and decreases the validity of any statistical analysis done with this data. There is no proof that these two months should be excluded, and no data is given on what crashes occurred during these two months to evaluate the validity of excluding this data. Only one other study that we have found on this subject purposely excludes the first months of RLC data like this(Delaware 2007). The use of control cities instead of control intersections in the same city(far removed from the RLC intersections) is also something that is not used in most other studies on this subject, and the failure to "separate the specific effects at treatment sites from citywide effects" in this study is criticized in the FHWA 2005 study on this subject. The lack of raw crash statistical data being cited does not allow for a more open analysis to confirm the conclusions of this study, but the conclusions are supported by the selective data that is provided.
This study is also criticized by the 2004 Greensboro Study, the 2004 Raleigh Study and the 2008 USF Analysis(in addition to the FHWA study already mentioned in the Comments). The authors of this study work for the Insurance Institute for Highway Safety(IIHS), an organization sponsored by car insurance companies which make substantial amounts of money on RLC installations due to points being assessed on drivers licenses and higher crash rates, both of which lead to higher insurance premiums, as well as direct investment by some insurance companies in the companies that sell Red Light Camera systems themselves, so they have a very strong vested interest in presenting RLCs in a positive light and cannot be considered a neutral or impartial party on this subject.