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Cary man plans suit over timing of yellow lights

Posted May 21, 2010

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— A Cary man claims that the formula used to set the length of yellow lights in town is flawed, which he says compromises safety and leads to tickets being issued unfairly at intersections with red-light cameras.

Brian Ceccarelli said he received a citation in the mail last year when a red-light camera caught him running a red light at Cary Towne Boulevard and Convention Drive. He said the incident frustrated him so much that he is crafting a potential class action lawsuit challenging the length of yellow lights.

Red-light camera sign Man claims yellow lights in Cary should be longer

"The shorter it is geometrically increases the number of people running the red light," Ceccarelli said.

The timing of the caution light is supposed to be based on the speed limit, the size of the intersection and a safe distance to stop.

Ceccarelli said that state Department of Transportation equations show the yellow light at Cary Towne Boulevard and Convention Drive should last 4.5 seconds, but he estimated it lasted only four seconds when he was ticketed.

"The half-second makes a big difference in the number of people that run a red light," he said. "It's a safety issue to everybody. By cutting short the yellow light, the town of Cary risks everybody's lives."

Cary traffic engineers and a physics professor at North Carolina State University dispute Ceccarelli's calculations.

Town officials said Cary's 17 red-light cameras are designed to prevent accidents. All yellow lights are timed to fit DOT safe-stopping standards, they said.

The red-light cameras in Cary generate about $100,000 in revenue from citations annually.

Ceccarelli said he believes the long-held yellow light timing calculations used across the country are wrong, and he said he hopes his lawsuit will bring the issue of traffic lights, math and safety to a head.

"They're all short anywhere from two to four seconds," he said. "They are not safe according to Newton's laws of motion."

28 Comments

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  • Subdivisions May 27, 1:44 p.m.

    "If cars never ever had to stop, would yellow lights exist?"

    Funny thing is that's a fantastic illustration of why this is so confusing to you. The light changing from green to yellow and the amount of time the yellow stays lit serve completely different purposes.

  • Alexia May 26, 5:52 p.m.

    Joe Schmoe, lights do not usually present a problem for me, but I can't say that I've never had a problem. I certainly have.

    What concerns me are those occasional times where it's hard to come to a stop. It happens to me every once in a while. Multiply that by hundreds of thousands of people who also have the occasional problem. Also consider the fact that different vehicles require longer stopping distances, the fact that some drivers are not as fast to respond to a light change as another person, etc. I can certainly see why there are accidents at intersections.

    I can't speak to whether the math is correct or not, but what it appears is that the math that is used assumes optimal, perfect driver performance. That's nonsense, since if everyone was an excellent driver all the time, there would never be accidents.

    So, at the very last, there ought to be some margin for error built into the formula.

  • ceccareb May 26, 2:31 p.m.

    Subdivisions: Think about this:

    If cars never ever had to stop, would yellow lights exist?

    Now revisit your premise.

  • Subdivisions May 25, 1:37 p.m.

    The safe stopping distance is _NOT_ based on the yellow interval, it's based on the speed limit and a comfy rate of deceleration. The grade of the approach might be a factor as well. Either way, there is no 'time' variable. Yes, you can figure out the time it will take a vehicle to stop over that distance, but that has no bearing on the duration of the yellow because that's NOT the purpose of the yellow interval.

    Alright, don't know how else to try and explain without getting really repetitive. Chances are good most of the Traffic profs at State have seen your website and would be happy to talk to you. You should consider it, they would obviously be much better at explaining this than I am.

  • Subdivisions May 25, 1:36 p.m.

    ceccareb - Your premise is still wrong. The yellow time doesn't apply to stopping vehicles.

    The the ONLY purpose of the duration of the yellow interval is to protect drivers who are inside the min safe stopping distance when the light turns yellow, to give them a safe and legal option. Those drivers are NOT expected to stop, they are expected to continue thru the intersection. At the speed limit. No deceleration. No averaging speed over the stopping distance.

    The duration of the yellow interval is meaningless to a stopping vehicle because *they are going to stop*. A stopping vehicle will continue to slow down regardless of the duration of the yellow, and will stop before entering the intersection.

  • Joe Schmoe May 25, 10:21 a.m.

    [continued...]

    I think the problem of running red lights is primarily due to drivers misunderstanding the basic purpose of a yellow light. This purpose is to notify the driver that the signal is changing so that s/he can perform a mental calculation of whether s/he can, given current speed, vehicle weight/condition/equipment, and distance to the intersection, stop safely before reaching the intersection.

    Drivers who misunderstand this purpose instead try to estimate the length of time they expect the light to remain yellow, and guess whether they can reach the intersection and slip through legally before the signal goes to red - a very dangerous approach to dealing with traffic lights, given that pattern settings may not be consistent. (I will be first to argue in favor of required consistency across the state or the country).

  • Joe Schmoe May 25, 10:19 a.m.

    Brian,

    Email to your address listed at the bottom of the derivation.pdf document on the redlightrobber.com website is bouncing. Don't know whether you were aware that address is bad.

    But on to my comment: I wonder if you've made an error in assuming a constant rate of deceleration for stopping cars. I've driven many times in all parts of Cary, have stopped hundreds of times at Cary stoplights, and have not once been forced by any combination of the laws of physics and the stoplight settings (or by anything else) to enter an intersection after a signal had gone to red. I generally dump a lot of speed early in my braking distance, and ease up on the brake as I approach the end of the stop.

    The lawsuit documents repeatedly state that people are "forced to run red lights" - but this has simply not been my experience in real life out on the roads in Cary.

    [More in next posting]

  • ceccareb May 25, 8:28 a.m.

    Subdivision's comment "The purpose of the yellow interval is to give drivers inside the minimum safe stopping distance enough time to get INTO the intersection before the light turns red." is the very physics make I am talking about.

    In the derivation of the equation the DOT and ITE use to determine the yellow interval, they mixed the physics properties of cars that do NOT brake ("time to get INTO the intersection") with an equation meant only for cars that brake. They mixed apples and oranges. They used the constant velocity of cars passing INTO the intersection; that is the speed limit, and applied it against a "braking" distance where a > 0 and the speed is not constant.

    That, THAT, is the nature of the physics mistake.

    By using the wrong speed, and that speed * time = distance, the DOT and ITE cut the once-safe braking distance in half. Now it's now longer safe. They literally force cars to run red lights. That fact shows up in the red light camera statistics.

  • ceccareb May 24, 7:44 p.m.

    I should have started with this:

    In law, there is a ruling that has been on the books for at least a 1000 years. It is called the King Canute ruling: It is obvious:

    "One cannot enact legislation that countermands the Laws of Nature."

    For example, President Obama cannot decree that the sun will not set. The Town Council of Raleigh cannot decree that acorns shall never fall from trees. The Town of Cary cannot decree that water shall never freeze.

    Any law based on such a decree is invalid, null and void.

    The DOT has decreed that the time it takes for a car to come safely to a stop is = v/2a. That countermands the Laws of Nature. It is v/a, not v/2a. Therefore the yellow light equation is invalid. Any laws enacted based on that equation, from the Canute ruling, are null and void. The operation of the red light cameras explicitly depends on that equation. Since the equation is null and void, so are the operation of red light cameras.

  • ceccareb May 24, 7:35 p.m.

    Like I said and you verified, the DOT gets the braking distance correct.

    BUT then the DOT divides the braking distance by the ***speed limit*** in order to get the yellow duration. The speed limit. "Dividing by the speed limit" should throw up a red flag for you.

    What is the average speed of a car decelerating at constant velocity from 45 mph to 0? It is 45 mph like the DOT says? No. It is 22.5 mph. You are ***decelerating***. Your average speed is half the speed limit. In order to get the time, the DOT should have divided the braking distance by v/2.

    The DOT cut the time in half.

    Now, most people learn this in elementary school:

    rate * time = distance.

    By cutting the time in half, the DOT CUT THE BRAKING DISTANCE IN HALF. The DOT's original braking distance was correct and safe, but once they divided it by the wrong velocity, they made it unsafe because rate, time and distance are interdependent.

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