City yields to longer yellow lights at four sites

By Kevin Flynn, Rocky Mountain News (Contact)

Published April 11, 2008 at 12:05 a.m.

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Denver will give drivers more yellow light time at four locations where it plans to put up red light enforcement cameras.

A Rocky Mountain News investigation showed that all four intersections have yellow lights that are too short, under an accepted engineering formula. One signal had less than the legal minimum. In many cities where this has been the case, red-light running and accidents have increased.

The city will increase yellow times, Denver Public Works spokeswoman Ann Williams said Thursday. It also will add pedestrian "countdown" signals at the four locations, which give the seconds remaining until yellow appears. Motorists often use such signals to know when the yellow will start.

Denver has generally used the legal minimum three seconds of yellow, although the law permits up to six seconds, depending on the speed of traffic. Under the engineering formula, three seconds is considered adequate for 25 mph traffic, but the four sites all have speeds higher than that.

The cameras are supposed to go live by mid-June on eastbound Sixth Avenue at Kalamath and Lincoln streets, westbound Eighth Avenue at southbound Speer Boulevard and northbound Quebec Street at 36th Avenue. The yellows should be up to 4.3 seconds under the formula.

Federal guidelines suggest that cities first take other measures, including a traffic-engineering study and increased yellow times, before opting for cameras. Denver didn't do such a study.

After the Rocky questioned traffic engineers about the issue, they developed a plan to better determine whether cameras are effective.

The city will identify four similar intersections, increase the yellow times at each, and monitor the effect on red-light running and accidents without the use of cameras, Williams said.

"We'll pilot this program for one year, and if we determine that the cameras are an effective way to increase safety, then we'll further explore their use in other locations in Denver," Williams said.

Some studies have found that cameras can increase accidents, typically rear-end collisions. That's because drivers tend to panic and brake too hard on yellow to avoid the $75 ticket, even when they are too close to the intersection to stop safely.

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