Official Title: A DETAILED INVESTIGATION OF CRASH RISK REDUCTION RESULTING FROM RED LIGHT CAMERAS IN SMALL URBAN AREAS
Authors: Mark Burkey, Ph.D. and Kofi Obeng, Ph.D.
This is a 2004 study by the Urban Transit Institute at the North Carolina Agricultural & Technical State University on the effects of red-light cameras in the city of Greensboro, North Carolina. This study compares the before and after crash statistics of 18 RLC intersections in that city. The study uses 26 to 35 months of pre-RLC crash data compared to 31 to 22 months of post-RLC data. The statistics used in this analysis are from the North Carolina Department of Transportation which used 100 feet as their Distance-From-Intersection inclusion zone for crashes. There are no significant data or conclusions in this report that suggest a reduction or increase in fatalities due to RLCs. Injury crashes were counted and did increase, but the study contains no raw data on injury crashes to back this up. The results show that crashes at RLC-equipped intersections have increased by 40% over the study period while crashes city-wide fell during the same time period. The study concludes that : "The results do not support the view that red light cameras reduce crashes. Instead, we find that RLCs are associated with higher levels of many types and severity categories of crashes."
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This is a detailed 60 page study, the data and statistical analysis appear valid. The selection of 18 RLC intersections is slightly above-average number of intersections for this kind of study. The use of 100 feet as the Distance-From-Intersection inclusion zone for crashes is close to the average for most states and below what the Federal Highway Administration uses. The before and after RLC date periods are sequential and more than adequate to provide a valid data set for comparison. There is a comparison of crashes at many control intersections in the same city which show a decline in total crashes over the study period. The conclusions of this study are mostly supported by the data supplied.
This study has a thorough analysis of several other previously released studies on the issue of RLC safety issues, and concludes that: "several studies have shown that RLCs usually reduce the rate of violations, very little evidence exists that confirms that RLCs reduce accident rates". Specifically the Oxnard, CA study is criticized in several ways: "The overall implication is that the effect attributed to the red light cameras by Retting and Kyrychenko is only a comparison of the accident growth rate between signalized and nonsignalized intersections in Oxnard, CA. The other data does not act as a control, nor does it add any information to this model."