By Kevin Flynn

Even after biting the dust, the Rocky is still performing public service — Denver has decided to adjust the timing of yellow lights at a total of 450 traffic signals around the city over the next two years, an outcome of our reporting last year on the start-up of the red-light ticket cameras.

What it means is that hundreds of drivers who were destined to get red-light tickets from police for doing nothing more than being trapped in the city’s own engineering deficiency will now proceed safely through intersections without facing a fine.

And maybe it will reduce the number of accidents at red lights.

It’s all because the Rocky took a look last year when Denver decided to erect cameras at four intersections where city officials say there were a lot of red light runners. Our finding, based on numerous studies of signal timing and reports from other cities that have used cameras, was that Denver was setting up a revenue bonanza from unwitting drivers who, despite driving safely otherwise, would be caught by short yellow times.

Denver was poised to spit out thousands of $75 tickets to people coming off the Sixth Avenue Freeway at Kalamath Street based on a three-second yellow light.

Federal law calls for yellow times between three and six seconds, and engineers recommend leaving the yellow light on longer when traffic is approaching at higher speeds. Denver’s practice had been to set yellows at the legal minimum of three seconds. Engineers consider that sufficient for 25 mph traffic, but in Denver, that was the standard at nearly all signals, even those with traffic approaching at 45 mph or faster.

Like most cities, Denver also adds an all-red safety phase of one to four seconds for cars to clear the intersection, but that doesn’t stop the criminalization of drivers who enter on red at the end of a yellow that’s set too short for driver expectation.

It boils down to this: The faster the traffic, the longer it takes to stop for a light. That’s just simple physics. And laws of physics will always trump laws of traffic, no matter whether a ticket camera is present or not.

We also reported that before Denver gave a red-light ticket camera contract last year to Redflex, an Australian outfit with U.S. headquarters in Scottsdale, Ariz., it didn’t follow the Federal Highway Administration’s guidelines that say cities should first try other measures, such as setting what’s called the “yellow change interval” for the existing traffic conditions.

Denver took our reports seriously enough to extend the yellow time at all four camera locations — and that’s already reduced the number of tickets by a tremendous margin, according to preliminary estimates.

We then reported in June last year that based on our stories, Denver decided to test the yellow-change hypothesis by doing a parallel study at four comparable intersections. As the ticket cameras were going live in July and August, a consultant put up video surveillance at those other test locations — and one other that was added later — where the city could monitor whether fewer drivers would run red lights just by adding more time to the yellow, without the punitive presence of ticket cameras and without telling drivers about the change. In other words, it tested normal driver behavior.

Preliminary results from that test show marked reductions in red-light violations at the unmarked locations compared with the ticket camera locations.

The vast majority of drivers react to a yellow light based on how fast they’re going relative to how close they are to the intersection, and not so much on whether they’ll get a ticket from a camera. Finding that “sweet spot” in the yellow timing that triggers optimum compliance is the key to safety.

The camera locations are Quebec Street at 36th Avenue, Sixth Avenue at Kalamath Street, Sixth at Lincoln Street and Eighth Avenue at southbound Speer Boulevard.

The test locations were Broadway and Eighth Avenue, Broadway and westbound Speer, Lincoln at Alameda Avenue, 15th Street at Champa Street and southbound Speer at Champa.

Denver Public Works is still massaging the data to remove some apples/oranges problems, but officials were sufficiently persuaded by the results that they already have begun adjusting yellow times around the city.

This year, 350 signalized intersections at which the speed limit is 40 mph or greater, along with some 35 mph intersections, will be adjusted.

Next year, another 100 signals at 35 mph intersection will be adjusted.

What the timing will be depends on each location. Unlike the previous policy, this won’t be one-size-fits-all. The city’s traffic engineering division will use a formula recommended by the Institute of Transportation Engineers that should result in longer yellow lights.

The only aspect of the city’s work I questioned was the use of the speed limit rather than the actual average speed of approaching traffic in calculations. Denver officials didn’t do a real-time speed survey to find out how fast cars are approaching the lights.

If you want to stop cars from crashing, you have to deal with how fast they’re actually going, not how fast you wish they were going.

Reach Kevin Flynn at kevin.j.flynn@comcast.net.