Missouri: Violations Still Down With Longer Yellows

The Newspaper
by The Newspaper

Photo enforcement advocates downplay the benefit of increased yellow time in addressing the problem of red light running. New evidence from Arnold, Missouri shows that red light cameras continue to flash at a much lower rate since the state mandated longer signal timing at a number of photo-enforced intersections.

Arnold was the first jurisdiction in the Show Me State to allow a private company, American Traffic Solutions (ATS), to mail traffic tickets to residents. Since 2005, ATS has handed out more than 30,000 tickets worth over $3.1 million. In 2010, tickets were being pumped out at an average rate of 800 per month. With longer yellows, that figure averaged just 113 through July and August using the most up-to-date data available.



Timing changes were made at and near the red light camera intersections. Yellows increased from 4.0 to 5.0 seconds at three intersections along Missouri Route 141 on February 24. Smaller changes were made on April 15, including a boost from 4.0 to 4.4 seconds at northbound 141 and US 61/67, a 4.0 to 4.5 second change at northbound US 61/67 at Rockport School, and from 4.0 to 4.7 seconds at southbound Vogel Road at Richardson Road (4.3 seconds at the northbound approach).

While a difference of 0.4 to 1.0 seconds in the length of the yellow light might seem insignificant, the extra margin of safety is critical. The vast majority of straight-through red light “violations” happen when a driver misjudges the end of the yellow light by less than 0.25 seconds — literally the blink of an eye ( view Texas Transportation Institute (TTI) chart). With those longer yellow times, the city and ATS are losing $780,000 in annual revenue — an 86 percent drop.

The Insurance Institute for Highway Safety’s former top researcher, Richard Retting, argued strongly against the use of yellow signal timing beyond the bare ITE minimum values. His research is cited by the Federal Highway Administration (FHWA) in its “Toolbox of Engineering Countermeasures,” which is used by cities to set up intersections prior to the use of automated ticketing machines.

“Present thought is that longer intervals will cause drivers to enter the intersection later and it will breed disrespect for the traffic signal,” the FHWA document explains. “The tendency for motorists to adjust to the longer interval and enter the intersection later is referred to as habituation. The before-and-after study by Retting and Greene evaluated the presence of habituation to the longer yellow… The authors concluded that habituation to the longer yellow did exist….”

Retting is now employed by a red light camera company.

[Courtesy: Thenewspaper.com]

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  • CarPerson CarPerson on Sep 26, 2011

    Blindly adding seconds is a half-assed way to correct short traffic lights in clear violation of the FHWA MUTCD. There is a formula. It is referred to as the Kell and Fullerton Light Duration Equation. The FHWA has a pamphlet you can download titled "Field Guide for Inspecting Signalized Intersections to Reduce Red-Light Running" (fguide_isirlr.pdf) It shows you how to use the formula to do the math for an intersection. 5.8 seconds covers 85% of all normal intersections. 4.6 seconds is about the shortest you come up with for a narrower intersection. Less than 4.6 seconds? Get a hangnail in the intersection and sue the city back to the beginning of civilization. Dick Retting is not someone I'd want involved in anything to do with signalized intersections.

  • Redav Redav on Sep 27, 2011
    The vast majority of straight-through red light “violations” happen when a driver misjudges the end of the yellow light by less than 0.25 seconds Here's the problem with this approach--it is based on a person's 'judgment' of when a yellow will end, in other words, it is his intention to run the yellow because he believes he can make it. What happens when drivers become accustomed to longer yellow lights? Will they add in that extra time to their judgment of whether they can make it? I don't know, but given my knowledge of how people gun it to make yellow lights, my guess is yes. (I've noticed that drivers whose first instinct is to stop at yellows don't bother 'judging' whether they can make it, but whether they can physically stop short of the intersection. Also, drivers with this attitude will look for clues for the end of the green light, such as cross walk lights changing, thus they are prepped for stopping before the light even turns yellow.) I disagree with having a private company operate RLCs. I disagree with them taking revenue from citations. I disagree with them having any say in light logic or durations. Yellow lights should be long enough for safety, but short enough that it is not a hindrance for traffic throughput. I would support a new concept of light that gives indication of how long it has left in its current state (e.g., how long before a red turns green, how long before a green turns yellow). Better information leads to better decisions. However, there are those who are not interested in making good and safe decisions, and a solution needs to be found that eliminates that form of thinking.
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