IDOT Opposing Bill To Enhance Traffic Safety?

Senator: Agency Against Longer Yellow Light Times At RLC Locations Despite Proof Of Safety Gains

The evidence is overwhelming.

At least according to Illinois State Senator Dan Duffy (R-Barrington).

That’s the reason Duffy says he introduced Senate Bill 3504–to try to improve the safety of Illinois intersections by adding one second or more of yellow light timing to traffic signals at red light camera locations.

Introduced February 8th, SB 3504, or the One Second For Safety bill, simply mandates municipalities or counties utilizing red light camera enforcement, use nationally recognized standards to determine yellow light timing for an RLC intersection and then tack on an additional second.

But, for some reason, according to Senator Duffy, the Illinois Department of Transportation, a state agency that has overseen impressive reductions in traffic accidents and deaths over the past decade through aggressive legislation, programs and initiatives promoting driving safety, is opposed to Duffy’s bill–despite a dearth of evidence to support such a measure.

“IDOT has come out and opposed the bill for ‘safety concerns’,” says Duffy. “I say that is an outrageous claim considering all studies show increasing yellow light times by one second drastically reduces red light running. I haven’t seen one study that refutes this. It’s mind boggling IDOT would oppose something that improves safety.”

Traffic Research Shows Impressive Results

Red light cameras have always been a very divisive topic.

Mainly because research studies trying to assess the effectiveness of RLC enforcement is pretty evenly split on the subject. Advocates for both sides of the argument routinely cite studies that strengthen their position while downplaying research which undermines their position.

But there’s no such division on the effectiveness of lengthening the yellow light interval at traffic signals. The research is overwhelming supportive of the concept. Studies researching the impact of lengthening the amber interval show reductions in red light running from 30%-92%.

For example, a 2007 study of Philadelphia intersections by the Insurance Institute for Highway Safety (IIHS) showed a 36% decrease in red light violations when longer yellows were employed.

The Texas Transportation Institute did a study in 2004, that according to its authors say, “An increase of 0.5 to 1.5 s(econds) in yellow duration will decrease the frequency of red-light-running by at least 50 percent.”

The “longer yellow” theory seems to hold up in real world practice as well. In late 2009, the town of Loma Linda, CA extended yellow light times on RLC intersections and saw a 92% reduction in red light violations.

Norcross, GA, had nearly the same results with an 80% reduction in red light running after the Georgia General Assembly passed a bill mandating amber intervals at all red light camera intersections be lengthened by one second. Ultimately, the local RLC program was dismantled due to the lack of red light violations because of the change.

And when red light running is reduced, reductions in crashes naturally follow.

A 2002 study by the IIHS “found that injury crashes at urban intersections fell 12 percent after the yellow and all-red traffic signal timing was modified according to ITE (Institute for Traffic Engineers) guidelines.”

So what’s behind IDOT’s opposition?

Duffy believes lobbyists for red light camera companies and municipalities know his bill, if enacted will reduce red light violations and subsequently reduce revenues derived by $100 fines for an RLC ticket.

“It looks like an extremely political move to me,” says Duffy. “Most people think adding one second of yellow is a logical solution. If it drastically improves safety regular people say ‘why not?’.”

City of Chicago traffic lights are set at the shortest federally acceptable level of three seconds, while many suburban intersections usually have four second yellows.

The Illinois Senate’s Transportation Committee will hold a hearing on the bill Tuesday, March 6th at 4 PM in room 400 of the State Capitol.

At press time, IDOT was still working on generating a response to this story.

Photo credit: Ian Britton and courtesy

24 Responses to IDOT Opposing Bill To Enhance Traffic Safety?

  1. DoR Employee says:

    “The Texas Transportation Institute did a study in 2004, that according to its authors say, “An increase of 0.5 to 1.5 s(econds) in yellow duration will decrease the frequency of red-light-running by at least 50 percent.”

    And would decrease the revenue generated at all RLC’s from municipalities outside of Chicago.

    The bad drivers in Chicago will still violate “No Turn on Red” and blow reds.

  2. DOR SB3504 covers all RLCs in Illinois including Chicago.

  3. Pete says:

    Supporters of red light cameras know they don’t make roads safer, but they don’t care. They just want the money.

  4. glg says:

    why would this bill only cover intersections with RLC’s? If it’s really about safety, why doesn’t it apply to *all* signaled intersections?

  5. Steven Vance says:

    I’d look beyond the IIHS and TTI and look for some research from non-industry sources like urban transportation centers at UIC, Northwestern, Rutgers, UC schools, as well as the Transportation Research Board.

    It seems weird to me to make legislation that would automatically tack on a second to whatever the national standard is (for Illinois). All signalized lights must follow the national standard unless they have an exemption. If it’s true that all research shows that a longer yellow increases safety (which I’m going to assume means reduced incidence of crashes and reduced crash severity), then the national standard should change.

    More studies on yellow light intervals at intersections:

    I’m curious to hear of a more detailed explanation from IDOT. Just throwing this out there, and playing devil’s advocate (I’m not a fan of IDOT except their crash data is pretty top notch), but maybe IDOT is concerned about throughput. Like, a longer yellow would reduce throughput. And IDOT is really in the business of moving cars, not actually facilitating “transportation”.

  6. Don says:

    This would be like taking the G-8 from Chicago. It might make sense and it might save lives but Rahm has already spent the money. It’s time we demand IDOT care more about safety and traffic flow than how to increase fines on citizens. Three of the top producing Red Light Cameras in Chicago are on one street on the South Side and brought in over $2,000,000 dollars last year alone.

  7. The Parking Ticket Geek says:

    Steve, some thoughts.

    1-TTI is based out of Texas A&M and is considered the premier transportation research institution in the nation.

    2-I checked out the Google link you listed and in the applicable studies on the first and second page either referenced the research I listed or agreed with the research I listed.

    3-Longer yellows actually increase throughput per the TTI study.

    4-I have yet to find a single study that claims a longer yellow light DECREASES safety. Not one. If someone can find me one, I will update the story–gladly.

    5-IDOT still has not got back to me with a response in regards to Sen. Duffy’s allegations.

    I think this could be telling. If IDOT is opposed to the 1 Second bill, I look forward to hearing what their rationale could be.

    But based on the research, the overwhelming research at that, I cannot see how IDOT (an agency that should be committed to improving safety) would be opposed to the bill.

  8. Mike says:

    Always remember that IDOT is only one “I” away from IDIOT as an old radio host would mention.

  9. The Parking Ticket Geek says:

    Nicely said Don.

    If you don’t know already, not one dollar of red light camera revenue has ever been specifically designated to improving traffic safety. All RLC revenue goes into the city’s general fund.

  10. There is one, and ONLY one, reason to oppose safer and longer yellow intervals on traffic lights. That reason is the predatory pursuit of $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ achieved at the expense of lower safety and higher accident rates overall.

    See the science on our website. James C. Walker, National Motorists Association,, Ann Arbor, MI (frequent visitor to Chicagoland and we just drove across Illinois today, coming from Missouri)

  11. Anne says:

    “Three of the top producing Red Light Cameras in Chicago are on one street on the South Side and brought in over $2,000,000 dollars last year alone.”

    Let me guess – Western, right?

  12. Bill McFarlin says:

    The “Federal Standard” is actually the “Kell and Fullerton 1998 Light Change Duration Formula”. Three seconds minimum? Only at the intersection of two 8-foot wide alleys. At a “normal” intersection 5.5 to 5.9 seconds is the normal baseline calculation. Please understand this is the BASE value before a number of adders are included by the traffic engineer.

    The third chunk of the K&F formula is the amount of time the Light Change Duration should be red to create an “all-red” condition.

    In 1958 a General Motors scientist published a paper that stated changing the right-of-way in 0.01 seconds is a prescription for a tragically unsafe intersection. You must have 2 seconds or so of an “all-red” to clear the conflicting traffic. In about 1974 the FHWA MUTCD finally acknowledged this fact. It has been part of the FHWA MUTCD ever since.

    Add the quick and dirty one second if you want but demanding a solid, honest adherence to the “K&F” formula and “All-Red” will give you stellar red light violation, traffic flow, accident avoidance maneuver, crash reduction and crash injury and property damage reduction numbers. Please consider going for this gold standard of intersection safety.

    Unfortunately, the plunge in red light violation revenue will expose wildly unchecked municipal spending. City and County governments are loathe to see that happen. Re-elections are ranked well ahead of signalized intersection safety by most, if not all, elected officials.

  13. The “gold” standard K&F is not used in most places in the world. ITE’s formula is. Nonetheless both standards are insignificant variations on Denos Gazis’ equation 9 in his 1959 paper “The Problem of the Amber Signal in Traffic Flow.”

    Traffic engineers systematically misapply both K&F and ITE formulas. The end result is federal standards which establish yellow light durations in opposition to the physical laws of motion. In other words, the federal standards force drivers to run red lights.

    I have written several papers on this topic, the latest one I will submit to Physics Today. Here is the latest draft:

    As for “adders”, if you are thinking about turning traffic, the proper yellow light duration as mandated by Newton’s Laws of Motion is not additive. K&F and ITE’s formula does not work for turning traffic at all.

    The 3 second minimum for turning traffic comes from an error in the 1994 ITE publication, “Determining the Vehicle Signal Change and Clearance Intervals.”

    I have pinpointed all the gross traffic engineer errors made to date in the above document. The red light camera companies and the City of Chicago use these errors to make a profit. And of course, the errors also kill people.

    If you want safe roads, then a few brave Chicagoans are going to have to challenge IDOT and the City of Chicago in a class-action lawsuit. Chicago is not going to give up their cash cow without such a fight. The argument is a physics argument, as I have described in the paper above. The argument is irrefutable. Traffic engineers cannot refute it. Matters of physics are not debatable. A judge can only decide in favor of it. In the end, all legislation which enforces standards in opposition to the laws of nature are illegal, null and void.

    The federal standards for setting yellow lights are illegal.

    There is no excuse. The laws of physics have been on the books since 1687. Traffic engineers, by not adopting the laws of physics, are malpracticing their trade. You can also sue the traffic engineers for malpractice. (Engineering is an application of physics. Get the physics wrong and you not practicing engineering.)

  14. Bill McFarlin says:

    Brian has done a tremendous service to those concerned about signalized intersection safety. His work continues to mature and his insights more sharply focused on true, honest, serious intersection safety issues.

    He does not mention it but the “problem” with the K&F formula and left turns is the formula presumes a known steady speed or a presumed steady deceleration to a stop.

    With a left turn, the approach speed is known but during a turn there is usually a substantial reduction in speed. The formula uses a snapshot of the approach speed, not the approximate turning speed, which throws the calculated value off. Also, a left turn “intersection length” can be considerably longer than the straight-through intersection length but some traffic engineers are not adjusting the intersection length and turn light change duration accordingly.

    If the traffic engineer is not catching and correcting for these “errors”, the K&F formula will indeed produce an erroneous result. Brian articulates these issues in some of his work.

    However, Brian is slower to acknowledge a properly skilled traffic engineer will include the appropriate adders, which underscores the fact that the K&F value is a BASELINE value.

    An example of another adder is an incandescent-to-LED conversion requires a 0.25 second adder. Delays in the traffic controller itself often require an 0.50 adder so the final calculated value is the actual value the driver sees. Unfortunately, as Brian points out, all too often all this is just blown off by City officials.

    Also, visualize a 30mph two-lane road crossing a 45mph 6-lane plus median Truck Route arterial. Far too commonly ALL FOUR APPROACHES HAVE THE SAME LIGHT CHANGE DURATION! Trial lawyers get custom-designed high-end vacation homes out of such gross traffic engineering negligence but cities keep doing it anyway out of stupidity, hubris, and/or revenue.

  15. B says:

    The standards for yellow light timing were altered when red light cameras were first developed a couple decades or more ago. They changed the duration of the yellow signal and allowed longer ‘all red’.

    The method to deal with an intersection with a red light running problem was also changed from ‘lengthen the yellow’ to ‘enforcement’. Lengthening the yellow was the method in the 1970s and it worked.

    Red light cameras (since the yellow shortening scam became widely known) are about finding intersections with various engineering defects from sight lines to signal timing and more and instead of identifying and fixing why a particular intersection has an issue a camera is put up to profit from it.

    It’s especially apparent when an RLC intersection only covers the approach where many drivers make a right on red.

  16. Dennis Smith says:

    I’ve recently received a “NOTICE OF VIOLATION” from Automated Enforcement, Tempe AZ.. This was for an intersection in the Village of Plainfield, Illinois
    I bought a stopwatch and timed the lights at all intersections from 95th Street to Rt. 126 on Rt. 59.

    The only thing that was a variant was the 135th intersection had RLC’s.

    The Timing on the yellow to green was about 2.7 seconds by my manual manipulation of the stopwatch.

    I’m going to fight it.
    The ITE Sandard say a minimum of 3 seconds in any speed zone.

    Any comments or help would be appreciated.

  17. Dennis Smith says:

    The one thing that is very important to note in the previous post, all other signals were longer on the yellow to red mode.

  18. Robert Weber says:

    For all the scholarly discussion that has taken place in this comment thread, I’m surprised that no one has mentioned this: In all the studies cited by the article, the yellow times before the additional second were below the ITE equation times. All of them. In fact, in a few cases it is specifically mentioned that the yellow times after the additional second were still less than the ITE equation. So, the question that needs to be asked is: how are the yellows in question currently timed? If they already use the ITE equations (a legal requirement where I practice in Virginia for RLC implementation), then adding one second will not make a significant difference in red light running.

  19. Dennis, contact

  20. Jon says:

    If everyone went the speed limit, this wouldn’t be an issue. Slow down and stop blaming the RLCs.

  21. David says:


    That’s just not true. As a bicyclist I am at risk in intersections every day. If the light is green when I enter the intersection, I should be able to get across it before it goes red. I often can’t at some of the longer intersections (like Lincoln, Damen, and Irving — and two of those streets have bike lanes so bicycles are expected to use that light….). I like the count downtimers for the cross walks. They give me a chance to judge if I have to stop while it’s still green… But we really must have proper yellow lengths.

  22. Josh says:

    As this article points out, there are better ways to promote safety in intersections than punitive measures. These include better timing of yellow lights, all signals being red for 1-2 seconds before a change in direction, and better signage and marking at problem intersections. All these measures are proven effective, and don’t require punishing otherwise good citizens and hurting the perception of local government by the citizens (which photo traffic enforcement does).

    I don’t feel safe around photo enforcement as it makes other drivers unpredictable, and I feel towns that use photo enforcement don’t use proper traffic engineering (too short yellow lights, speed limits below the 85th percentile, speed limits that go up and down for no apparent reason, poor signage, poor intersection and lane markings). I stopped going into the city for shopping/restaurants awhile ago for these very reasons.

    Thank you Dan Duffy for all your hard work. And this is coming from someone who usually votes Democrat.

  23. william cunningham says:

    One second! Just makes PHOTOSHOPING a larger project. If anyone has to make a right on red, Open your door & say one than close it. AT LEAST IF THEY PHOTOSHOP that you will remember what really happened. It is a great magic trick, But not worth a $100.00.

  24. william cunningham says:

    I forgot a bought the reduced accident theory. If you take a shortcut thru an alley and get robbed you do not go in that alley again. The proponents of red light are looking at results, but giving he wrong interoperation.

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