• Red Light Camera MYTH

Guy W. Midkiff
February 27, 2008
Red Light Camera Myth

The following is the result of a large statistical study done on red light cameras (RLC’s). While many communities make anecdotal claims of magical reductions in accident rates at intersections, these results are most often self-serving and anything but scientific. I am only paraphrasing the entire document of several hundred pages. You are welcomed to go to the North Carolina A&T State University School of Business and Economics to download the full study. (click here to download entire pdf file )

Executive Summary

This paper analyzes the impact of red light cameras (RLCs) on crashes at signalized
intersections. It examines total crashes and also breaks crashes into categories based on both severity (e.g., causing severe injuries or only property damage) and by type (e.g., angle, rear end). Prompted by criticism of the simplistic methods and small data sets used in many studies of red light cameras, we relate the occurrence of these crashes to the characteristics of signalized intersections, presence or absence of RLC, traffic, weather and other variables.

Using a large data set, including 26 months before the introduction of RLCs, we analyze reported accidents occurring near 303 intersections over a 57-month period, for a total of 17,271 observations. Employing maximum likelihood estimation of Poisson regression models, we find 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.

An overall time trend during the study indicated that accidents are becoming less frequent, about 5 percent per year. However, the intersections where RLCs were installed are not experiencing the same decrease. When analyzing total crashes, we find that RLCs have a statistically significant (p<0.001) and large (40% increase) effect on accident rates. In addition, RLCs have a statistically significant, positive impact on rear-end accidents, sideswipes, and accidents involving cars turning left (traveling on the same roadway).

The one type of accident found to experience a decrease at RLC sites are those involving a left turning car and a car traveling on a different roadway. When accidents are broken down by severity, RLCs were found to have a statistically significant (p<0.001) and large effect (40-50% increase) on property damage only and possible injury crashes. There was a positive, but statistically insignificant estimated effect on severe (fatal, evident, and disabling) accidents.

These results run contrary to the many studies in the RLC literature. Previous studies have sometimes found an increase in rear-end accidents, but often find offsetting decreases in other types of accidents. While this study incorporated many advances in methodology over previous studies, additional work remains to be done. Because accident studies rarely use a true experimental design and data are not perfectly observable, additional careful study of RLCs is warranted to verify our results.

*This is an update to the October 2003 version of this report. Using the latest available data, we include an additional 12 months of accident data. Additionally, several data coding errors were discovered in the original data set, and corrected for this report. Therefore, results from the October 2003 report should be disregarded.

1.1 Problem Statement
Nearly half of all accidents in the U.S. occur at or near intersections (US DOT, 1999, p. 50). Consequently, many studies have been conducted that relate various aspects of intersections to safety and accident rates to develop improvement strategies. One such strategy is automated enforcement of traffic signals using cameras, i.e., red light cameras (RLCs), which has been suggested and used in some cities to reduce red light running. The potential of these cameras in reducing accidents and improving safety have been reported in few studies, with most studies reporting mixed results. For example, Retting et al. (1999a), Retting and Kyrychenko (2002), and Milazzo et al. (2001), using before and after data found RLCs reduce crashes at intersections. On the other hand, Andreassen’s (1995) longitudinal study spanning a 10-year period found reductions in crashes at high accident sites and increases in crashes at low accident sites. McFadden and McGee (1999) add another twist in their review of studies on automated enforcement of red light running.

While accepting reductions in violations and cost savings as benefits, they suggested that improved methodology and more data are needed to validate and quantify the effects of RLCs on crashes, thus casting some doubts on prevailing views on the benefits of RLCs.

The following gives one of the best studies I have yet read on RLC’s:

If you haven’t already done so, please read highwayrobbery.net’s Home page

Back to highwayrobbery.net’s Links page

Cong. Armey’s Website & His Report: “The Red Light Running Crisis – Is It Intentional?
___________________________________________________________ Also, if you follow the following link, you will find one of the better arguments against RLC’s. I will caution the reader that the link will take you to an ACLU website, where the data was compiled. As a disclaimer, I have major philosophical differences with this organization, but I do believe the information, there, to be accurate. CLICK HERE

For another report, go to the Washington Post: DC Red Light Cameras fail to Reduce Accidents.


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