NMA E-Newsletter #150: Plenty of Questions, Few Clear Answers

City officials in Green Cove Springs, Fla., probably didn’t think anyone would notice when they made small reductions in yellow-light durations at a few city intersections.

Well, an energetic reporter with The Florida Times-Union did notice and started asking questions.

Why were the yellow lights shortened just before red-light cameras were installed at those intersections, he asked? What could possibly be behind such a change?

With surprising candor, city and state officials acknowledged the changes but explained they were made “to bring timing in line with national guidelines.”

For example, at an intersection with a posted speed of 30 mph the yellow time was reduced from 3.5 to 3.2 seconds. Another with a posted speed of 35 mph was reduced from 4.0 to 3.6 seconds.

A Florida Department of Transportation (FDOT) spokesperson explained that the new times are based on standards from the Institute of Transportation Engineers (ITE) that factor in speed and reaction time.

But are they really?

The ITE formula uses the actual speed of the approaching vehicle (typically the 85th percentile speed) for determining the proper yellow light interval.

FDOT is no doubt plugging in the posted speed, but because those limits notoriously understate the prevailing speed of traffic, the resultant yellow light interval will always be lower than what the ITE has deemed as safe. (For more on the ITE formula, visit the NMA’s shortyellowlights.com website.)

If FDOT doesn’t want to go to the expense of conducting traffic engineering studies to properly determine the approach speeds, we have a simple solution.

Go ahead and plug the posted speed limit into the ITE formula, but then add one second to the calculation. That adjustment will account for a 10 mph gap between the speed limit and the vehicle approach speed, a fairly typical differential.

After all, a comprehensive study from the Texas Transportation Institute found that “an increase of 0.5 to 1.5 s in yellow duration (such that it does not exceed 5.5 s) will decrease the frequency of red-light-running by at least 50 percent.”

For safety’s sake, why not be generous in establishing the duration of the yellows?

Here are some more questions:

If the original yellow times fell within ITE standards why did they need to be changed? And, if standardization was the goal, why not change yellow-light times at all intersections in Green Cove Springs?

Part of the answer may lie in the following numbers: According to The Florida Times-Union article, since February, the red-light cameras have generated $850,000 for city and state coffers, as well as $105,000 for American Traffic Systems (ATS).

Another part of the answer may come from the contract between camera company ATS and the city of Green Cove Springs.

A recent report from the Public Interest Research Group found that many red-light camera contracts require cities to cede control of yellow-light timing and other traffic engineering decisions to the camera companies.

We don’t know if this is true for Green Cove Springs, but our energetic reporter is on the case.

Green Cove Springs is the first city in this part of the state to install red-light cameras, but nearby Jacksonville is close to inking a deal as well.

Here is a call-out to our Jacksonville-area members: Send a copy of this newsletter to the city’s mayor and council. Phone them and voice your opinion.

Let them know that revenue generation should never trump intersection safety.

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