The Problem is the International Standards
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Misapplied Physics in the International Standards that Set Yellow Light Durations Forces Drivers to Run Red Lights This paper describes the formula, what it does and how today's traffic engineers mispply it. This paper also presents red light camera citation data showing how minor changes in yellow light durations dramatically and permanently affect red light running counts. |
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Derivation of the ITE Yellow Change Interval Formula This is a paper shows the mathematical steps to get to the yellow change interval formula. The paper describes the physics and the assumptions along the way. |
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Dos and Don'ts of the Yellow Change Interval Formula This a letter from Professor Alexei Maradudin, the last surviving inventor of the ITE Yellow Change Interval Formula. (July 2013). By every DOT doing the don'ts, every DOT demands drivers to break the unbreakable laws of physics, a demand which is physically unattainable thus forcing drivers to run red lights. |
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The Problem of the Amber Signal Light in Traffic Flow Gazis, Herman and Maradudin (GHM) co-authored this paper in 1959. In 1965 ITE miscopied this paper's equation 9 into its Traffic Engineering Handbook. By omitting GHM's "Analytical Considerations", ITE has been instructing traffic engineers to abuse this formula for over 50 years. For example, applying this formula to turning movements shorts the yellow light by 2 to 4 seconds forcing millions of turning drivers to run red lights each day. |
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Determination of Left-Turn Yellow Change and Red Clearance Interval The American Society of Civil Engineers (ASCE) Journal of Transportation Engineering published Dr. Chiu Liu's paper in 2002. This paper is the follow-up work to Gazis, Herman and Maradudin. Dr. Chiu Liu's formula computes the minimum yellow duration which allows all traffic to move legally. Chiu's formula is equation 13 on page 454. No jurisdiction implements the formula as stated and thus causes millions of drivers to run red lights inadvertently. |
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Field Tests for Right-Turn Movement This video is from the New Orleans Regional Traffic Safety Coalition (NORTSC). Steve Strength, a professional engineer and ITE certified traffic engineer who works for the LaDOTD, presents the case from an engineer's prespective that the ITE yellow change interval does not provide enough time for right-turn movements. Field test measurements carried by the coalition (including several police departments) require 6.2 seconds for vehicles to make the right turn, a value outside the maximum limit of the MUTCD standard. The MUTCD is wrong. |
Preexisting Condition - Yellows Are Short Already
People should know that red light cameras only exploit a preexisting condition. Cities do not need to short their existing yellow lights to make lots of money. The yellows are already short by international standard.
Jurisdictions like Winnipeg, Canada or New York City that pride themselves with not complying to the ITE formula serving up yellow lights which are shorter than the formula have a bigger problem. The ITE Formula does apply physics. The ITE Formula applies physics to satisfy one singular type of traffic situation which represents the fastest possible yellow time. All other traffic situations, including turning situations, demand more time than the ITE formula.
The Problem is with the Yellow Light
Everyday when confronted with a yellow light we ask, "Should I stop? Should I go? Should I beat the light? Should I slam on the brakes? Do I have time to make the turn? Am I going to run this light by a fraction of a second?" To us these questions are part of everyday driving. We do not give them a second thought, until we get a red light camera ticket. We must understand that it is the nature of the yellow light which gives birth to our questions. The yellow light poses predicaments which though we are familiar, we cannot solve correctly 100% of the time. Our failure to solve sometimes ends up by us unintentionally running a red light. Sometimes the yellow light even poses a unsolvable situation which forces us to run a red light. All the predicaments, situations and even the questions themselves rise from mathematical formula traffic engineers use to set the length of yellow lights.
Traffic engineers use the the ITE formula to set yellow lights. The formula sets the yellow time to 50% of the time it takes a driver to stop his vehicle. 50%. We want to change the formula so that it gives the driver 100% of the time. Because some drivers think that yellow light means stop, they will stop aggressively causing a rear-end collision. Some will skid into the intersection on a red. For some drivers who go instead of stop, yellow light means "go really fast." While we poke fun at that definition in movies like "Starman", that definition is actually the truth. You will find that definition in the 1982 ITE publication Transportation and Traffic Engineering Handbook.
It is necessary to have faith in traffic engineers, but we learned in the last three years that that expectation is not warranted. Despite the life-and-death responsibility they have with setting yellow durations, traffic engineers (as a profession) do not know how to set a yellow light. They all misunderstand the formula. The ITE formula is like a picture, a picture worth a thousand words. Those words are in the language of physics, a language which traffic engineers do not understand. At this web site's North Carolina Exhibits section, you can read the depositions and affidavits of 4 NCDOT traffic engineers. 4 of 4 did not know where "v" is supposed to measured. 4 of 4 do not know that the formula cannot be applied to turning movements. 4 of 4 did not know that this formula creates dilemma and indecision zones. 4 of 4 did not recognize that this formula is not an equation of motion, a physics term meaning that one cannot apply this formula to objects in the universe and expect it work. 3 of 4 did not know that the ITE formula embeds the safe stopping distance formula. 1 of 4 could not same a single one of Newton's Laws of Motion, and believes that "Physics only applies to a partially vacuumed Earth."
The ignorance of the ITE Formula extends beyond the borders of North Carolina. The ignorance is all over the world. The ignorance even extends to the highest levels. It extends to the National Transportation Board. The November 2012 report NCHRP-731 exhibits this ignorance. Written by Hugh McGee, Sr., Keven Moriarty, Kim Eccles, Mindy Liu, Timothy Gates and Richard Retting, these authors represent typical traffic engineers. These authors make the same mistake. They misapply the ITE formula to turning movements. Read their treatment for left turning drivers. Then compare it with our paper The Derivation of the Yellow Change Interval Formula. The physics of the ITE formula plainly does not apply to turning traffic.
We found that the Courts are not the venue to resolve problems of physics. We had sued the Town of Cary over these issues. The case went on from 2009 to 2013. The trial ended January 17, 2013 with the Court ruling in favor of Cary. The judge signed the Order and Judgment on March 4, 2013. Judge Paul Ridgeway presided. Ridgeway ruled that the Town of Cary can financially exploit the errors of the NCDOT, that legitiate engineering practices can contain errors both typographical and scientific, and that physics is irrelevant to the motion of objects. So long as Cary was abiding by the North Carolina General Statutes, even though those Statutes contradict the Laws of Physics, Cary could not be held culpable. In my opinion, Judge Ridgway strained out the gnat and swallowed the camel.
We decided not to appeal. Because Paul Ridgeway did not understand the physics and showed that he could easily be mislead by a traffic engineer who knows no better and is protecting his own reputation, we could only expect the same from appellate judges. It is bewildering to the physicist that his own government does not understand the basic laws of physics well-established in 1687. It is as if the court system lives in the Middle Ages.
Source of Red Light Camera Revenue
Cary, North Carolina told by Chad Vader
This is an account of the red light camera program that existed in the Town of Cary, North Carolina. Dr. Moley represents the real-life person Brad Hudson. Hudson came to work once a month and without looking at the videos, accused and convicted everyone of running a red light. Baby Cookieflex plays the part of Maria, an employee of Redflex. She worked at the "Safelight" office in Cary. If you have a problem with the ticket, the Cary police send you to Maria or Frank Rubino. Maria indeed said, "Aren't you happy that your $50 goes to public schools? Don't you care about children?" Until the very end of the program, Cary had spread Redflex's propaganda line to the local TV stations and the newspapers. Cary never said what percentage goes to schools. By contract, the Town of Cary paid Redflex $49.50 of every $50. That is 99%. That leaves 50 cents to the schools. The contract contained a tiered compensation clause. When the Town of Cary and the NCDOT engineers forced more drivers to run red lights, Cary only had to pay Redflex 60%. Once Cary took out its own administrative costs, about $5.00 out of $50.00 went to the schools.