by brian » Tue Mar 02, 2010 11:16 pm
A study of the effects of Red Light Cameras from a Feb 2005 FHWA study
Safety Evaluation of Red-Light Cameras was performed by Council, Persaud, Eccles, Lyon, Griffith
From the 2005 study:
- What effect do RLCs have on intersection safety (i.e., intersection crashes) at monitored intersections versus intersection safety throughout the jurisdiction?
The results of empirical Bayes crash-frequency analyses at the treated intersections indicate that RLCs have effects similar in direction but somewhat smaller in magnitude than those indicated in past studies. Right-angle crashes (the surrogate for "red-light-running" crashes) decrease significantly and rear end crashes increase. - Table 17 shows the combined results from all seven jurisdictions, indicating a 24.6 percent reduction in total right-angle crashes and a 15.7 percent reduction in right-angle (definite) injury crashes.
(Note: KABCO Scale. K = Killed. A = disabling injury. B = evident injury. C = possible injury)
Total rear end crashes increased by 14.9 percent, and rear end (definite) injury crashes increased by 24 percent.
While the results varied some across the seven jurisdictions, the direction and degree were remarkably consistent, particularly given the differences in crash-reporting practices between jurisdictions.
In summary, the multijurisdiction database developed and the crash-based and economic analyses used made it possible to answer most of the questions posed by FHWA. This economic analysis represents the first attempt in the known literature to combine the positive effects of right-angle crash reductions with the negative effects of rear end crash increases, and to identify factors that might further enhance the effects of RLC systems. Larger crash sample sizes would have added even more information. The following primary conclusions are based on these current analyses:
- Even though the positive effects on right-angle crashes of RLC systems is partially offset by negative effects related to increases in rear end crashes, there is still a modest to moderate economic benefit of between $39,000 and $50,000 per treated site year, depending on whether one examines only injury crashes or includes PDOs, and on whether the statistically non-significant shift to slightly more severe right-angle crashes remaining after treatment is, in fact, real.
- Even if modest, this economic benefit is important. In many instances today, the RLC systems pay for themselves through red-light-running fines generated. However, in many jurisdictions, this differs from most safety treatments where there are installation, maintenance, and other costs that must be weighed against the treatment benefits.
- The modest benefit per site is an average over all sites. As the analysis of factors that impact showed, this benefit can be increased through careful selection of the sites to be treated (e.g., sites with a high ratio of right-angle to rear end crashes as compared to other potential treatment sites) and program design (e.g., high publicity, signing at both intersections and jurisdiction limits).
table17.jpg
KABCO Scale. K = Killed. A = disabling injury. B = evident injury. C = possible injury
See the FHWA study
Safety Evaluation of Red-Light Cameras
A study of the effects of Red Light Cameras from a Feb 2005 FHWA study [url=http://www.tfhrc.gov/safety/pubs/05048/index.htm]Safety Evaluation of Red-Light Cameras[/url] was performed by Council, Persaud, Eccles, Lyon, Griffith
From the 2005 study:
[list][*]What effect do RLCs have on intersection safety (i.e., intersection crashes) at monitored intersections versus intersection safety throughout the jurisdiction?
The results of empirical Bayes crash-frequency analyses at the treated intersections indicate that RLCs have effects similar in direction but somewhat smaller in magnitude than those indicated in past studies. Right-angle crashes (the surrogate for "red-light-running" crashes) decrease significantly and rear end crashes increase. [list]Table 17 shows the combined results from all seven jurisdictions, indicating a 24.6 percent reduction in total right-angle crashes and a 15.7 percent reduction in right-angle (definite) injury crashes.
(Note: [url=http://www.ecs.umass.edu/umasssafe/PDFS%20for%20Site/CODES%20LD%20-%20fact%20sheet.pdf]KABCO Scale[/url]. K = Killed. A = disabling injury. B = evident injury. C = possible injury)
Total rear end crashes increased by 14.9 percent, and rear end (definite) injury crashes increased by 24 percent.
While the results varied some across the seven jurisdictions, the direction and degree were remarkably consistent, particularly given the differences in crash-reporting practices between jurisdictions.
[/list]In summary, the multijurisdiction database developed and the crash-based and economic analyses used made it possible to answer most of the questions posed by FHWA. This economic analysis represents the first attempt in the known literature to combine the positive effects of right-angle crash reductions with the negative effects of rear end crash increases, and to identify factors that might further enhance the effects of RLC systems. Larger crash sample sizes would have added even more information. The following primary conclusions are based on these current analyses:
[list][*]Even though the positive effects on right-angle crashes of RLC systems is partially offset by negative effects related to increases in rear end crashes, there is still a modest to moderate economic benefit of between $39,000 and $50,000 per treated site year, depending on whether one examines only injury crashes or includes PDOs, and on whether the statistically non-significant shift to slightly more severe right-angle crashes remaining after treatment is, in fact, real.
[*]Even if modest, this economic benefit is important. In many instances today, the RLC systems pay for themselves through red-light-running fines generated. However, in many jurisdictions, this differs from most safety treatments where there are installation, maintenance, and other costs that must be weighed against the treatment benefits.
[*]The modest benefit per site is an average over all sites. As the analysis of factors that impact showed, this benefit can be increased through careful selection of the sites to be treated (e.g., sites with a high ratio of right-angle to rear end crashes as compared to other potential treatment sites) and program design (e.g., high publicity, signing at both intersections and jurisdiction limits).[/list][/list][attachment=0]table17.jpg[/attachment][url=http://www.ecs.umass.edu/umasssafe/PDFS%20for%20Site/CODES%20LD%20-%20fact%20sheet.pdf]KABCO Scale[/url]. K = Killed. A = disabling injury. B = evident injury. C = possible injury
See the FHWA study [url=http://www.tfhrc.gov/safety/pubs/05048/index.htm]Safety Evaluation of Red-Light Cameras[/url]