Judging Driver Behavior by Intuition or by Facts?

By Gary Biller, NMA President

Investigative reporter Noah Pransky of Tampa Bay TV station WTSP filed an explosive report earlier this week about the intentional shortening of yellow-light intervals at red-light camera intersections for the purpose of raising ticket revenue. Pransky noted that of the more than $120 million of photo ticket revenue collected across Florida in 2012, $50 million was directly attributable to red-light camera program operators setting yellow lights too short.

That is a startling number, particularly for those who aren’t familiar with the multitude of documented accounts of short yellow lights that the NMA has gathered over the years. More alarming still is that the combination of red-light cameras and improper yellow-light timing creates the dubious double penalty of inflating ticket revenue while simultaneously making intersections less safe.

A common counter claim against lengthening yellow-light cycles is that drivers will eventually adjust to the conditions and go back to their supposed natural instincts of playing “let’s beat the light.” Both Florida State Senator Jeff Clemens and Charles Territo, chief propagandist of camera vendor American Traffic Solutions, voice this in Pransky’s report.

That is not an uncommon position for pro-camera legislators and camera company employees to make. Some of the public jump on that bandwagon because it makes intuitive sense to them that motorists can’t help but push the margins, whether it be ignoring the speed limit or following an urge to zip through intersections at the first sign of a yellow light, safety be damned.

This view of kamikaze drivers is not only intuitively incorrect, it is factually wrong. Several studies have shown this:

“The data show that the percentage of last-to-cross vehicles clearing the intersection (T + 0.2) seconds or more past the yellow onset was not appreciably changed by the extension of the yellow phase.”

The Influence of the Time Duration of Yellow Traffic Signals on Driver Response, Stimpson/Zador/Tarnoff, ITE Journal (November 1980)

“Research has consistently shown that drivers do not, in fact, adapt to the length of the


Determining Vehicle Change Intervals – A Proposed Recommended Practice,Institute of Transportation Engineers (1985)

“Drivers do adapt to the increase in yellow duration; however, this adaptation does not undo the benefit of an increase in yellow duration.”

Effect of Yellow-Interval Timing on Red-Light-Violation Frequency at Urban Intersections, Bonneson/Zimmerman, Texas Transportation Institute (January 2004)

Several communities, from Gwinnett County, Georgia, to Loma Linda, California, and places in-between, have put this to the test by analyzing intersection safety statistics in the months and years after lengthening their yellow lights by 0.5 to 1.0 seconds. Violation rates typically plummet 50 to 90 percent almost immediately, and have been shown to remain at those low levels years after the fact.

If you hear a state legislator or city official trying to justify the use of short yellow lights in conjunction with a red-light camera program on the basis of “it doesn’t matter, drivers can’t help themselves,” don’t let them get away with it. Your fellow drivers and your wallet will thank you.

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