Benefit

Red light violation cameras significantly reduce rates of red light running at ticketed intersections and those in the same travel corridor.

A study of twelve intersections in Northern Virginia.


January 2013
Arlington County,Arlington,Virginia,United States


Summary Information

Critics of red light violation cameras argue that the cameras are installed for the purposes of generating revenue for the jurisdiction, not for the safety benefits. This study was conducted by the Insurance Institute for Highway Safety (IIHS) in order to determine the safety benefits of using red-light violation cameras at signalized intersections, measured by reduction in the rate of red-light violations per 10,000 vehicles. The study was conducted in Northern Virginia, in Arlington and Fairfax counties and included twelve signalized intersections in 2010 and 2011.

Methodology
The twelve study intersections were categorized in four groups: four with red light cameras (camera group), two intersections without cameras on the same corridor (corridor spillover group), two intersections without cameras on different travel corridors (non-corridor spillover group), and four intersections without red light cameras in Fairfax County (control group). The count and severity of the red light violations were captured over three, two weekday periods; during the warning period (July 2010), one month after ticketing began (August 2010) and 13 months after ticketing began (August 2011). Severity was categorized into three groups: >= 0.5 seconds, >= 1 second, and >= 1.5 seconds.
The rates of observed red light running violations per 10,000 vehicles were computed for each study group for each severity for each time period. Logistic regression models were used to estimate the effects of red light cameras on the probability of red light violations of each severity at the intersections.

Findings
The results of the study show that there were significant reductions in violations at camera-enforced intersections. Reductions in rates were greater as the violation severity level and time after deployment increased. Spillover benefits were only observed for intersections along the same travel corridors as the camera-enforced intersections, but those results were not always statistically significant. A year after ticketing began at the intersections with enforcement cameras, the odds of a red light violation occurring at least 1.5 seconds after the light turned had decreased 86 percent, relative to what would have been expected without the cameras. Violations of at least one second and 0.5 seconds were reduced by 48 and 39 percent, respectively. The results for violations of at least 1.5 and 0.5 seconds were statistically significant, while the results of violations of at least 1.0 seconds were marginally statistically significant.

While many benefits were seen at the camera intersections, the corridor benefits were only significant in the initial period after ticketing began. The number of violations in the non-corridor intersections rose significantly after ticketing began. The authors were unable to explain why there was an increase in violations. The study authors suggest that a larger and more widely publicized program is needed to achieve community-wide benefits, rather than the localized benefits seen in the camera equipped intersections.

See Table 3 below for more detailed information about the results of the logistic regression models of changes in the odds of red light violations. See Table 2 in the study for more detailed information on the changes in red light violation rates for the study intersections.


Violations 0.5 second or more after red
Violations 1 second or more after red
Violations 1.5 seconds or more after red
Study GroupStudy Period
Percent change in odds of violation
p value
Percent change in odds of violation
p value
Percent change in odds of violation
p value
Effect of red light cameras at camera intersections (interaction between camera vs. control intersections and after vs. warning period)1 month after ticketing
-17.7
0.423
-16.5
0.664
-83.3
0.014
1 year after ticketing
-38.6
0.047
-48.4
0.073
-86.1
0.006
Effect of red light cameras at corridor non-camera intersections (interaction between corridor spillover vs. control intersections and after vs. warning period)1 month after ticketing
-44.9
0.047
-29.4
0.418
-77.9
0.049
1 year after ticketing
-14.0
0.569
-24.8
0.465
-62.6
0.178
Effect of red light cameras at non-corridor non-camera intersections (interaction between non-corridor spillover vs. control intersections and after vs. warning period)1 month after ticketing
116.8
0.079
467.6
0.038
8.4
0.938
1 year after ticketing
127.5
0.059
477.4
0.030
22.2
0.843
Table 3: Summary of results from logistic regression models of changes in the odds of red light violations 1 month and 1 year after red light camera ticketing compared with warning period and relative to control non-camera intersections. (Statistically significant results are in bold, while marginally significant results are in italics.)

Benefit Comments

No comments posted to date

Comment on this Benefit

To comment on this summary, fill in the information below and click on submit. An asterisk (*) indicates a required field. Your name and email address, if provided, will not be posted, but are to contact you, if needed to clarify your comments.



Source

Effects of Red Light Camera Enforcement on Red Light Violations in Arlington County, Virginia

Author: Anne T. McCartt and Wen Hu

Published By: Insurance Institute for Highway Safety

Source Date: January 2013

URL: http://www.iihs.org/research/topics/pdf/r1185.pdf

Rating

Average User Rating

0 ( ratings)

Rate this Benefit

(click stars to rate)


Goal Areas

Safety

Typical Deployment Locations

Metropolitan Areas, Statewide

Keywords

photo enforcement, red light cameras, red light running, automated enforcement, traffic signals, run red lights, RLR, red light runners, photo-red, red light signal enforcement, signal violation, traffic camera

Benefit ID: 2013-00826