Safety Benefits of Yellow Timing Increase Documented in Denver

The Newspaper
by The Newspaper

A Rocky Mountain News investigation reveals that Denver city officials and police made no effort whatsoever to track the performance of their public safety program (a.k.a. red light cameras) beyond counting the 11,200 tickets worth $840,000 that had been issued between June and November. Redflex Traffic Systems, the Australian company that operates the automated ticketing machines at four intersections in return for a cut of the profits, did not submit a single report to the city regarding maintenance or calibration of the cameras, despite being required to do so by contract. The city only requested these documents after the Rocky Mountain News made an inquiry to follow up on the program’s performance. Doh! Another interesting discovery: increasing the duration of the yellow signals has had a greater safety impact than the use of red light cameras in Denver, Colorado. That’s the conclusion of a

In May, the same newspaper had forced Denver to increase the duration of yellow at the camera-monitored intersections by documenting how the city used yellow times of 3.0 seconds and under– violating federal law in at least one case. At the posted 45 MPH intersection of northbound Quebec Street and 36th Avenue, the yellow increased from 3.0 to 5.0 seconds. Yellow rose from 3.0 to 4.0 seconds at both eastbound Sixth Avenue at Kalamath and westbound Eighth Avenue at Speer Boulevard. Yellow increased just half a second at eastbound Sixth at Lincoln Street to 3.5 seconds.

At the first three locations, Redflex had tested the number of “violations” that happened at each intersection when the yellow light was set to last 3.0 seconds, counting 125 in a 12-hour period. With the longer yellow, the new police data show a daily average of between nine and sixteen violations in a 24-hour period; a drop of approximately 90 percent. This matches the long-term benefit of longer yellow documented after a similar lengthening took place at a Fairfax County, Virginia intersection. The camera at Sixth and Lincoln experienced less of a benefit– an average of 53 daily violations– after receiving the smallest increase of 0.5 seconds of extra yellow.

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  • Pch101 Pch101 on Jan 14, 2009
    it’s basic common sense I didn't ask you to repeat your argument. I asked you to support it with some sort of evidence. As noted, you don't have any. if people run red lights on purpose today, what incentive does a longer yellow give them to suddenly become law-abiding? Again, that misses the point. The fact remains is that study after study demonstrates that a light of appropriate length increases compliance. You have not proven that to be wrong, not at all. The issue here is with compliance rates. That's how rational people measure results. The studies show improve compliance with appropriate timing. So I have no idea what your objection is. If there are standards for light timing, there is no good reason to avoid using them. If the compliance rates increase, there is no reason to dispute the outcome.
  • M1EK M1EK on Jan 16, 2009

    No, Pch, you haven't posted squat backing up your theory either - the TTI study showed that 50% of people complied right away, but did not track long-term compliance. That still leaves 50% of people who don't comply, which would, to an honest man, suggest a combination of yellow times + cameras.

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