In 1959, the Institute of Transportation Engineers (ITE) developed the formula for the optimal length of time for the yellow traffic signal. The formula was created such that it would allow a motorist driving at the legal sped limit enough time to determine whether to proceed through the light or to stop the vehicle. Since then, times, and timing, have changed.
Tweaking the Timing
The dispute over the timing of yellow signal lights has been going on for many years. In 2001, a report issued by the U.S. House of Representatives Majority Leader asserted that changes the ITE had made to the formula for signal timing, which was done to aid in the use of red light cameras, created a “red light running crisis”.The ITE’s 2012 proposal encouraged increasing the timing of yellow lights for motorists moving directly through intersections, but it also encouraged shorter times for those signals used to facilitate right or left-hand turns. Additionally, it allowed local municipalities to lower the speed limit of turn lanes by 5 mph, which completely throws off the application of the original timing formula for signals.
The Man With the Plan
In early August 2015, the ITE held a conference in Hollywood, Florida, where they were informed by one of the original authors of the formula, Alexei Maradudin, that the ITE’s proposed recommendations misapply that formula in many instances, resulting in shorter signal times which directly affect the decision making process for drivers approaching those signals.According to Mr. Maradudin, who is currently a University of California physics professor, when it comes to drivers who are making a turn at an intersection, the formula cannot be applied properly because of the need for a driver to slow down to make the turn. The formula does not take that into consideration, so it cannot be applied properly. A separate mathematical formula which takes into account the decreasing speed of the vehicle must be used to determine the correct timing for those signals.
Stop Playing Around
Even if the speed limit for turning lanes is decreased by 5 mph, the math just doesn’t work. In fact, according to Joe Bahen, a licensed engineer for the National Motorists Association, there is no plausible basis for reducing the speed limit in those cases where the main speed limit is no higher than 35 mph.Figuring out the right formulas for traffic signal timing isn’t something the average person is going to do. This is a job for those who have the knowledge to do it correctly, and those people are members of the ITE. It has been proven time and again that a difference of less than one second in the timing of a yellow light can make a huge difference in the number of red light camera tickets issued from intersection using the cameras. So perhaps it’s time for the professionals to listen to their own members, the ones who calculated the original formula in the first place, and stop tinkering with what works.