Benefit

In Chicago, red light camera enforcement systems reduced overall injury-producing intersection crashes by 10 percent.

Chicago DOT experience with red light camera enforcement


January 2017
Chicago; IL; Chicago; Illinois; United States


Summary Information

The City of Chicago has one of the longest-running and largest red light camera (RLC) enforcement systems in the country. While numerous studies have shown that camera enforcement is an effective deterrent to reckless driving and its use improves overall roadway safety, support for its application in various cities has not been uniform. Specifically, its application in Chicago has continued to generate public debate. This study performs an assessment of Chicago’s RLC program in terms of its impact on traffic safety, leading to a set of best practices in RLC enforcement, and recommendations for further improvement to the Chicago program. The aim is to provide guidance for continued RLC operation at individual camera locations, as well as for selection of locations for future implementation. By investigating available historical data and conducting statistical analyses, performance metrics and a set of guidelines were proposed to ensure the program is being implemented to the best benefit of the general public and of the City. A stakeholder engagement strategy was also designed and implemented to take into account expert and public opinion on the RLC program. The stakeholder outreach effort sought to better characterize and understand the expert and lay person perceptions of public concerns and gaps in knowledge about Chicago’s RLC program.

METHODOLOGY

For the purpose of this study, 340 sites before and after the RLC system deployment (years 2008 and 2009), referred to as the treatment group, were analyzed. Another 236 sites, where no cameras were installed, served as the control group, thereby providing a basis for the comparative effectiveness assessment.

This study designed and implemented a methodology for an observational before-after assessment that considered regression-to-the-mean (RTM) as well as potential spillover effects. Regression to the mean is the statistical tendency for locations chosen because of high crash histories to have lower crash frequencies in subsequent years even without treatment. Spillover refers to the impact of RLC enforcement on reducing crashes at non-camera intersections, through its impact on driver behavior. Both of these phenomena have not been systematically accounted for in previous studies. The study used a state-of-the-art Empirical Bayesian (EB) statistical methodology for the observational before-after study. In this approach, EB statistical simulation methods and actual observations are used to predict the crashes in the after period had there been no RLC treatment.

Furthermore, the study performed an analysis of RLC violations over time to understand and quantify the contributing effect of traffic features, intersection factors, and signal configuration on the frequency of violations. Regression models were used for that purpose, using violations at 152 RLCs in the City of Chicago over a 6-year period between 2010 and 2015.

FINDINGS

The Empirical Bayesian (EB) before-and-after analysis method was applied to the cameras commissioned in 2008 and 2009 in the City of Chicago. The results are in general agreement with the findings in the literature, that the RLC treatment reduces angle and turn crashes (by 19 percent in Chicago), and increases the rear-end crashes (by 14 percent) with an overall reduction in injury-producing* (see Notes) intersection crashes (by 10 percent). Angle and turn crashes are both more severe, and about three times more frequent than rear-end crashes (in the before RLC period), and thus the primary target of safety enforcement at signalized intersections. The study also documented significant spillover effect (positive impact on safe behavior) from RLC installation.

Notes

*Injury-producing crashes included all crashes resulting in one or more of the following (KABC): killing, A-type (incapacitating), B-type injury (not incapacitating), or C-type (possible) injury.

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Source

Chicago Red Light Camera Enforcement: Best Practices and Program Road Map

Author: Mahmassani, Hani; Joe Schofer, et.al.

Published By: Chicago DOT

Source Date: January 2017

Other Reference Number: ISBN: 978-0-9978889-1-1

URL: http://www.transportation.northwestern.edu/research/report-redlightcameras.html

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Goal Areas

Safety

Typical Deployment Locations

Metropolitan Areas

Keywords

photo enforcement, red light cameras, red light running, automated enforcement, traffic signals, run red lights, RLR, red light runners, photo-red, Traffic safety, Red light enforcement, Crash analysis, Driver behavior, Signalized intersections, Public policy

Benefit ID: 2017-01137