Study: Red Light Cams Improve Safety, Have “Spillover Effect” on Other Intersections

A red light camera at Irving Park and Clark. Photo: John Greenfield
A red light camera at Irving Park and Clark. Photo: John Greenfield

While red light cameras have been proven to save lives in other cities, in recent years Chicago’s program has come under constant criticism. Some of it has been warranted, such as the Chicago Tribune’s investigative series that exposed a bribery scheme involving former camera vendor RedFlex and Chicago Department of Transportation official John Bills. Other attacks have been off-base, such as the Tribune’s claim that the cameras had no safety benefits because they increased the incidence of rear-end collisions with injuries, which largely ignored the fact that the cams reduce the number of T-bone crashes, which are much more likely to result in serious and fatal injuries.

The red light camera program became a major issue in the last mayoral elections, when challenger Chuy García promised to shut down all the cams if elected. In response Mayor Emanuel promised a number of reforms to the program, including the removal of 50 cameras at 25 low-crash and the installation of pedestrian countdown signals at the 42 out of the city’s 174 red-light camera intersections that didn’t currently have them. Both of those tasks have essentially been completed.

As part of the reform process, the city hired Northwestern University’s Transportation Center to conduct an independent study of the red light camera program and make recommendations for improving it. The report, released today, confirmed that the cameras have significant safety benefits, resulting in an overall ten percent drop in injury crashes. It also noted a never-before-documented “spillover effect” that is also resulting in less red light running at intersections that don’t have the cams.

The study was led by Transportation Center director Hani S. Mahmassani and included input from an advisory panel of traffic safety countries from around the country. “Quantitative studies conducted in this project demonstrate significant safety benefits of the current [Chicago red light camera] program,” the report stated.

The 104-page study also identified six intersections out of the remaining 151 locations where cameras have issues a large number of tickets, but there has been no corresponding drop in crashes. It identified criteria for predicting where installations are most likely to be effective in improving safety, including traffic volume, geometrics of the intersection, evidence of a high number of T-bone and turning crashes, and low number of rear-end crashes.

In response the city plans to relocate cameras from these six intersections to locations where it is believed they can do more good.

Here are the intersections proposed for camera removal:

  • 95th Street & Stony Island Avenue (2 cameras)
  • Western Avenue & 71st Street (2 cameras)
  • Western Avenue & Pershing Road (2 cameras)
  • Grand Avenue & Oak Park Avenue (2 cameras)
  • Irving Park Road & Kedzie Avenue (2 cameras)
  • Peterson Avenue & Pulaski Road (2 cameras)

And the intersections proposed for camera installation:

  • Wacker Drive & Lake Street (2 cameras)
  • Michigan Avenue and Jackson Boulevard (2 cameras)
  • Dearborn Avenue & Grand Avenue (2 cameras)
  • Central Avenue, Foster Avenue, Northwest Highway & Milwaukee Avenue (4 cameras)
  • Pershing Road and Martin Luther King Drive (2 cameras)

Per city ordinance, CDOT will hold public meetings to discuss the proposed changes before any cameras are taken down or installed. Notably, three of the proposed new locations are downtown, which currently has few traffic cams.

Beverly resident and transportation advocate Anne Alt, a Streetsblog freelancer, said the removal of the cameras at Western and Pershing could be problematic since the intersection is “an exceptionally hairy one due to high speeds and poor sight lines.” Alt added that sight lines are even worse at 95th and Stony, but she hasn’t heard of many crashes there.

The report also found that enforcing red light violations that occur within a microsecond of the instant a light turns red might not provide many safety benefits. The study recommended extending the enforcement threshold for issuing a violation from the current standard of 0.1 seconds to up to 0.3 seconds after the light turns red. It argued that thus change would maintain the safety benefits of the program while making enforcement fairer. The researchers said there’s a “dilemma zone” faced by otherwise law-abiding drivers who are forced to make a split-second decision on whether to stop or keep moving through the intersection when the light turns red.

In response, the city will immediately extending the “grace period” for violations up to 0.3 seconds. CDOT says this is a longer interval than exists in many other cities with red light cams, and the same as the policy in New York and Philadelphia.

In addition to the overall finding that injury crashes dropped by 10 percent thanks to the cams, the study found that while rear-end crashes increased by 14 percent at intersections where cameras were installed, consistent with other cities, the more dangerous T-bone and/or turning crashes decreased by 19 percent. Unlike the Tribune, the report noted that federal research has shown that T-bone crashes have a lost productivity cost to society that is about five times greater than the cost attributed to damage from rear-end crashes.

As for the “spillover effect,” the Northwestern researchers compared before- and after-crash data at 85 intersections where cameras were installed in 2008 and 2009 with crash data for 103 intersections that didn’t get cameras.

“I am pleased that this comprehensive report confirms the beneficial safety impact of Chicago’s red light camera program,” stated CDOT commissioner Rebekah Scheinfeld in a news release. “The goal now is to continue our ongoing effort to increase transparency and accountability for the program by embracing the study’s recommendations.”

It’s good to hear that the effectiveness of red light camera enforcement, which has been proven by numerous studies elsewhere, has been corroborated by the Northwestern report on our local program. It also sounds like the planned changes are a step in the right direction towards making Chicago enforcement more effective and fair.

  • kastigar

    What needs more enforcement is the “No Turn on Red” signs. These signs are
    often ignored, and at many other locations cars slow down, but don’t stop, at
    the red light. They just roll on through. Right-turn-on-red should be
    eliminated at every intersection in the city.

  • David Henri

    I agree 100%. Just eliminate the right turn on red.

  • Lakeview Guy

    This study has no merit. I doubt it was “independent”. It should talk about setting the yellow lights at 4-5 seconds. Bottom line is that accidents (not crashes) increase at these intersections. And we know the program was built using bribes and there was no justification for many of the intersections that have cameras. This is an example of one of the most poorly run programs in the world. The entire program should be stopped immediately.

  • Lakeview Guy

    Rebekkah should also point out that Northwestern receives over $3.2 million in city contracts. They certainly wouldn’t want to lose that. Again, this study is complete garbage, so let’s hope this isn’t research that is trotted out whenever the city (or other cities) want to drum up support for “automated enforcement”. I can’t wait to see the garbage the vision zero strategy suggests.

  • johnaustingreenfield

    More on the yellow light issue:

    The bottom line is *not* the total number of collisions. Yes, the camera intersections saw a 14 percent uptick in rear-end collisions resulting in injuries, an issue that lengthening the post-red grace period for ticketing from 0.1 seconds to 0.3 seconds will help address.

    But, in keeping with Federal Highway Administration research on red light cams in various cities, the Northwestern study found that Chicago’s cams reduced reduced T-bone collisions by 19 percent. While rear-end collisions are generally fender benders involving minor injuries, T-bone collisions are much more likely to result in serious injuries or fatalities because cars offer little protection from side impacts.

    Not only did the NWU find a ten percent decrease in injury collisions overall, the fact that T-bone collisions decreased significantly means there was an net drop in fatalities, serious injuries, lost productivity, and property damage.

    “Accidents (not crashes) increase at these intersection.” You’re arguing that when two motor vehicles collide it’s not a crash? Sounds like you need to start a new hashtag, #AccidentNotCrash.

  • Carter O’Brien

    What are the specific issues you have with the report? The methodology?

  • Jacob Wilson

    So ultimately they reduce harm and fatalities but increase property damage. Just like roundabouts. I think Americans hate both for the same reason: ‘muh private property’ is more important than actual lives.

  • 1976boy

    Just wanna keep running red lights with no consequences, huh?

  • Lakeview Guy

    The conflict of interest
    it should have been conducted by a completely independent third party

  • Carter O’Brien

    Northwestern is a completely independent third party. “Independent” is not the same thing as “free of influence,” you’ll need to demonstrate something a lot closer to a quid pro quo (or that the City in some way improperly influenced the report) to make the claim stick that the results have been doctored to appear more favorable to the City.

    It’s published and publicly available – if the actual research is flawed, people will catch it. It will just take more work than simply making assumptions and pointing fingers.

  • Carter O’Brien

    The cameras actually catch the rolling stops.

  • Lakeview Guy

    Thanks – I’ll be sure to make sure traffic reporters refer to “crahses” as accidents. Wait – I have a job and more important things to do with my time than harass the media on twitter.

  • Lakeview Guy

    Ha – I do sometimes. you should have seen me the other morning when I was running late to the airport. I think I ran 2 or 3 lights. Thankfully there isn’t much traffic at 5:30 am. I can also get to about 50 or 55 MPH on city streets! :)

  • johnaustingreenfield

    I promise that I will never tell any of my media colleagues to refer to crashes as “crahses.”

  • planetshwoop

    I am in favor of the cameras — I agree that there is a network effect on driving from having them in place that is beneficial.

    The criticism that cameras are in effect a tax on drivers in the form of a penalty strikes me as somewhat fair. It’s hard to separate the safety benefits from the financial benefits that accrue to the city from bad behavior.

    (And yes, I drive, and yes, I understand that it’s possible to avoid the fines by not breaking the law. But Chicago has enough mistrust in this area that I think the concerns are somewhat legit.)

    I wonder if some of the criticism changes if a portion of the funds received from red-light cams go to visible improvements in the areas where they are placed: murals on via ducts, pothole fixes, improved crosswalk paint, etc. etc. One has to be careful on how to construct the program so people don’t feel like by violating safety they’re donating money to improvements, but by actually *seeing* something change might affect the perception of the program.

    (I am kind of obsessed with these painted intersections in Portland, esp. if they could be combined with way-finding for bikes/peds.

  • Guy Ross

    I’m at a loss to see how an automated system of compliance enforcement is either a trust building or trust busting process.

    Do turnstiles at L stations which you can either pay or jump also fit this criticism?

  • Guy Ross

    You just stick to doing it on comments sections of selected media whose stated purpose is to make streets safer for all users.

    Much better use of your time….

  • planetshwoop

    Automated enforcement has been beset by problems since its inception. There have been a barrage of legit scandals (bribery) and useless noise (Tribune hyper-ventilating about yellow lights). It faces frequent criticism from alderman and media, which is absolutely trust busting.

    It is seen as a way to get revenue from citizens — this is obvious from it’s ongoing presence as a campaign issue. It is a false dichotomy that we are choosing between safety and revenue; both are goals of the program. Yet the revenue piece is deeply resented. (And apparently with some reason: the non-tax revenue has gone up 40% since 2010, and while this includes building permits and parking tickets, undoubtedly a decent chunk is automated enforcement.)

    Seeing effects of the revenue would likely change the perception.

    Automated enforcement has been in place for close to 10 years (I think?). It’s obviously not going away but is still seen as illegitimate by a large group of citizens.

  • gsm32

    I have finished reading through and analyzing this Northwestern Red Light Camera study on Chicago that was released a few days ago, and there are quite a few problems with it:

    First, the 2 year gap in the data collection is not a standard practice in a study like this and no reason is given for ignoring this data. This very large gap in the data greatly reduces the significance of the conclusions. Related to this, they spend a great amount of space in this report discussing how they will account for regression to the mean, yet they chose relatively short data periods. They could have easily used two additional years of before and after data, as well as removing the 2 year gap which would have enabled them to be able to have up to 6 years of both before and after crash data. They provide no reasons for their limited data range choices.

    Second, this study ignores Property-Damage-Only(PDO) crashes completely, in spite of frequently using the phrase “Total Crashes” they never explicitly mention in any of their conclusion sections that it really only means total injury-only crashes.

    Third, the “Documentation Research” ignores results in those studies that do not fit their apparently pre-conceived conclusions. For example, they mention the 2007 Virginia Transportation Research Council report but they only state that there was an increase in rear-end crashes and a decrease in “red light running” crashes while completely ignoring that total crashes went up 23% and injury crashes went up 17% in that study. The 2005 University of Arizona study they mention shows similar numbers for increases in total and injury crashes within Phoenix as well, yet those results are not mentioned either. Also, almost all of the studies cited analyzed true total crashes, including PDO crashes, while this report did not, making for an invalid comparison of this report to the studies cited in the literature review. Overall, the literature review is inconsistent and their summary of the literature review is not accurate given the conclusions of the studies cited.

    Fourth, they appear to equate “red light running” crashes with “angle” crashes, while the two crash types are not the same since angle crashes contain a very significant proportion of failure-to-yield crashes that do not involve red light running.

    Fifth, they collected crash data from the Chicago Department of Transportation(CDT), which they say originally came from the Illinois Department of Transportation(IDOT). They never state why they didn’t just get the crash data directly from IDOT. This is significant because the 2010 University of Illinois at Chicago study showed that there were very significant differences between the IDOT and CDT crash data, because the CDT data excluded any crashes outside of 25-50 feet from the intersection while the IDOT data allowed for crashes up to 150-300 feet from the intersection.

    Sixth, they do not include any of the raw crash data on a per-intersection basis, meaning that there is no way to validate their calculations or replicate the analysis because only the totals and summaries are shown. In fact, they don’t even provide lists of the 85 RLC intersections and 59 non-RLC intersections that they chose to perform the crash change analysis on.

    All of these issues put together greatly degrade the significance of this report.

  • Guest

    Stony & 95th is a very high crash intersection. That said, that doesn’t mean that the cameras are the solution there.

  • kastigar

    It’s only seen as illegitimate by those car drivers who speed or run red lights.

  • kastigar

    Then what solution to the problem at Stony and 95th do you suggest?


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The Chicago Tribune’s David Kidwell and his colleagues have written extensively about the city’s red light camera program. Some of that reporting has been constructive, including revelations about the red light cam bribery scandal, unexplained spikes in ticketing, and cameras that were installed in low-crash locations during the Richard M. Daley administration. Other aspects of the […]