The Problem is the International Standards

Blinded By The Truth

Does the Multibillion-Dollar Red Light Camera Sector Owe Its Existence - and Profits - to Traffic Engineers' Misapplication of the Yellow Change Interval Formula?

Traffic Technology International published this cover story in its October/November 2013 issue. This story summarizes much of the literature on this website. An engineer making an intersection safe never means he made the intersection such that it allows traffic to move legally.

Science Proves Yellow Lights too Short

Red light Camera Traps: Does Science Prove Our Yellow Lights Too Short?

CBS WTKR, Channel 3, Hampton Roads, VA: February 5, 2014.

"The Institute of Traffic Engineers miscopied the yellow change interval formula into its 1965 engineering handbook. Traffic engineers, the so-called experts, do not know the math and science behind their own formulas."

Derivation of the ITE Yellow Change Interval Formula

Derivation of the ITE Yellow Change Interval Formula

This is a paper shows the mathematical steps to derive yellow change interval formula from scratch; that is, from Newton's Second Law of Motion. The paper describes the physics and the assumptions made along the way.

Misapplied Physics Profits Red Light Camera Companies

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.

Yellow Change Interval Dos and Donts

Dos and Don'ts of the Yellow Change Interval Formula

This a letter (July 2013) from Professor Alexei Maradudin, the last surviving inventor of the ITE yellow change interval formula. Every Department of Transportation in the world does the don'ts which cause drivers to inadvertently run red lights.

The Problem of the Amber Signal Light in Traffic Flow

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.

The Problem of the Amber Signal Light in Traffic Flow

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.

This paper is peer-reviewed.

The beginning of the paper states explicitly that the turn lane yellows must be longer than the straight-through.

No DOT makes the turn lane yellows longer because traffic engineers do not understand the physics of the ITE formula. Traffic engineers think drivers go slower in the turn lane and thus deduce that the yellow can be shorter. But traffic engineers do not know that the yellow light duration is all about how long it takes to traverse a fixed distance. That fixed distance is the distance it takes to comfortably stop your car from the maximum allowable speed. The slower a driver goes, the longer the yellow must be.

That misunderstanding of the physical sciences is enough to convict every traffic engineer in the United States and Canada for violating the local statutes for professional engineers. Every State and Province requires that a professional engineer must possess and apply the knowledge of the mathematical and physical sciences necessary for his job.

Field Tests for Right-Turn Movement

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 perspective that the ITE yellow change interval does not provide enough time for right-turn movements. Field test measurements carried out by the coalition require 6.2 seconds for vehicles to make the right turn, a value longer than the maximum limit of the MUTCD standard.

Uncertainty in the Yellow Change Interval

Uncertainty in the Yellow Change Interval

Red light cameras enforce imprecise engineering precisely. What is the uncertainty in the yellow change interval? Should law enforcement be aware of this uncertainty and grant the driver the tolerance required by the underlying engineering?


Television Newscasts

Science Proves Yellow Lights too Short

Red light Camera Traps: Does Science Prove Our Yellow Lights are too Short?

CBS WTKR, Channel 3, Hampton Roads, VA: February 5, 2014.

WTKR. Newport News Re-evaluates Yellow Times

Newport News Re-evaluating Yellow Light Times after NewsChannel 3 Investigation

CBS WTKR, Channel 3, Hampton Roads, VA: February 7, 2014.

WTKR - Redflex has Violation Calculator

Redflex Tells Local Cities Where to Put Cameras Based on ‘Violation Calculator’

CBS WTKR, Channel 3, Hampton Roads, VA: February 19, 2014.

WTKR proves what we suspected. Redflex knows physics too. Given the predictable failings of the ITE yellow change interval formula, Redflex wrote a violation calculator to compute exactly where the engineering failures produce the most revenue.


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. 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. In spite of 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 misunderstand the formula. The ITE formula is like a picture and a picture is worth a thousand words. Those words are in the language of physics, a language which traffic engineers apparently 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 drivers to conform to it. 3 of 4 did not know that the ITE formula embeds the safe stopping distance formula. 1 of 4 could not name a single one of Newton's Laws of Motion and believes that "physics only applies to a partially vacuumed Earth."

The misunderstanding of the ITE Formula extends beyond the borders of North Carolina. It extends to the National Transportation Board. The November 2012 report NCHRP-731 explicitly exhibits this misunderstanding. 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, Dr. Chiu Liu's paper Determination of Left-Turn Yellow Change and All-Red Clearance Interval and the original paper on the amber signal, The Problem with the Amber Signal Light in Traffic Flow and recent letter by the inventor of the yellow change interval formula himself, Dr. Alexei Maradudin.

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 began in 2009 and the trial ended January 17, 2013 with the Court ruling in favor of Cary. The judge, Paul Ridgeway, signed the Order and Judgment on March 4, 2013. Ridgeway used a local ordinance to trump the laws of physics. Ridgeway ruled that the Town of Cary can financially exploit the errors of the NCDOT, that legitimate engineering practices can contain errors both typographical and scientific, and that physics is irrelevant to the motion of cars. As long as the NCDOT abided by its own practices, correct or not, Cary was not responsible for its ineptitude, even though Cary's own traffic engineers confessed to some of the issues.

We decided not to appeal. Because Ridgeway is a well-respected judge, we felt that we could only expect the same ruling from appellate judges. It bewilders the physicist that the court does not recognize the laws of physics. It is as if the court operates 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 had a problem with the ticket, the Cary police sent you to Maria or to 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 Safelight 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 for approaches which had less than 120 violations per month. 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 caused more than 120 drivers to run red lights per months for an approach, Cary had to pay Redflex 60%. Once Cary took out its own administrative costs, about $5.00 out of $50.00 went to the schools.