By on September 19, 2011

[Editor’s note: The following was sent to us by Donald Sawicki of, a site where Mr Sawicki offers insight and literature on radar and red light camera safety issues to victims, defendants and legal professionals.]

The first step towards determining if a red light camera exists to make money is to answer the question: Does the traffic light force drivers that just happen to be in the wrong spot (worst case) when the light changes yellow to brake safely (worst spot at worst time)? If the answer is “safe braking for worst case” the camera probably exists for legitimate reasons of safety. If the yellow light forces unsafe or even dangerous worst case braking, the camera is strictly a source of money (a dangerous tax) that goes to cities or states and equipment suppliers (which typically split the booty). To catch (trap, trick, hook or crook) more redlight runners some municipalities shorten the yellow time forcing drivers (even NEAR worse case distance) to run the light. It gets worse: many jurisdictions use outdated driver reaction times (some established over half a century ago) when determining yellow duration, resulting in short yellow light times and unsafe worse case braking.

There are a number of reasons a large number of stoplights have too short yellow times’. One reason is when stoplights (3 color system patented in 1922) were introduced in the first half of the 20th century (when vacuum tubes were new) reaction times were “estimated” to be 1 to 1.5 seconds — stilled widely used in the early 21st century. In 1999 a detailed controlled study (on a controlled track and in a driving simulator using licensed drivers with various skill levels) determined average driver reaction time to be 2.3 seconds. California uses 2.5 seconds, the National Safety Council (NSC) and Great Britain use 3.0 seconds.

Another reason for short yellow times is many intersections that have been improved and changed (widened, crosswalks added, lane usage changed, etc.), some multiple times, were not reevaluated for yellow duration (an oversight or mistake). Another common error is a speed limit is increased but yellow times stay the same (and now too short for the increased speed).

A second more or less can make a huge difference between safe and dangerous braking. At the beginning of 2011 the Missouri Department of Transportation (MoDot) started reevaluating and adjusting all state controlled traffic light yellow times. MoDot is serious about public safety. So far MoDot has increased yellow duration’s ranging from 0.3 seconds to 1.3 seconds. This summer one ot the traffic lights reevaluated and yellow time increased had a redlight camera. Red light runners dwindled to a trickle from over 1500 per month to less than 20 per month, a 99% DROP!

A traffic light’s safety can be subjectively established using a few measurements and a little mathematics. Only 5 parameters are needed to determine worse case braking; speed limit, road grade, yellow light duration, distance from “stopline” to “in the clear”, and driver reaction time. Knowing just these 5 factors a signal light’s worse case braking (and safety) can be objectively established and degree (or lack) of safety.

Speed limits are usually posted, road grade is 0 for flat level terrain. Yellow light duration is best measured with a video camera and counting yellow light frames. Stop to clear distance varies with intersection and state. In many states the official “Rules of the Road” cite something to the effect “When the red light appears, you may not enter the intersection”*, setting the clear line at the cross-street curb line. *From Illinois Rules of the Road.

The mathematical formula for traffic light timing is widely published (the Institute of Transportation Engineers – ITE for example). The formula calculates yellow light time, by rearranging the formula deceleration can be obtained to get worse case braking. Once worse case deceleration is established an intersection’s safety can be subjectively determined and compared (light, moderate, hard, driver maximum, dangerous or vehicle maximum braking).

How to Safety Rate Redlight Cameras” discusses in detail the parameters (and formulas) involved, and has an online calculator that computes braking action given speed, road grade, stop-clear distance, yellow duration, and (a safe for EVERYONE) driver reaction time (2.3 seconds minimum recommended). 

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15 Comments on “How To Tell If A Red Light Camera Is A Safety Tool Or A Dangerous Form Of Taxation...”

  • avatar

    This article needs some serious proofreading. It’s barely readable – I gave up trying.

    • 0 avatar

      Somebody (and by “somebody” I mean the author of this article) really (as in very much so) needs (but probably doesn’t “want”) to stop (cease, halt, discontinue) using (or writing) parenthetical (a long word that basically means “with parentheses” (parentheses are the curvy things around the clauses that the author should have just left out)) statements (like this one).

      • 0 avatar

        This guy needs to understand the difference between “objectively” and “subjectively”. I think he means “objectively”. Poor grammar detracts from the subject of the article and renders it indefensible under argument. JMHOFWIW

  • avatar

    While on vacation in Denver, stayed in a suburb that had redlight cameras, can only conlude that safety isn’t the purpose of them. I spent way to much time watching the lights and often hit the brakes hard (ABS kicked in). I should have been watching traffic. The yellows were shorter than around here, and never had red at all 4 lights. I’m fairly sure that my wifes Glacier National Park license plate frame that covers the state saved me a ticket. Light changed to yellow just as I was entering the intersection making a left turn, but I maintained a safe distance between the car in front of me. That was the last time I was safe at an intersection.

  • avatar

    I thought it was quite interesting, and did not have any trouble reading it.

  • avatar

    BOTH the green AND yellow lights are shortened. Any article that does not discuss how the green light is to be set is shortchanging the reader.

    4.6s is about as short as the light change can be. Below that, you are dealing with an unusual intersection. 5.8 seconds covers 85% of all intersections. A city using 5.8 seconds is a pretty cool place to drive.

    The legacy “all yellow” traffic signal plan results in intersection conflict by as much as 1.5 to 2.0 seconds. Using an “all-red” traffic signal plan, WHICH IS REQUIRED IN ALL “PERMISSIVE YELLOW LAW” SITUATIONS results in a separation of 0.75 to 2 seconds, all but eliminating intersection conflict. Cities not using it are in violation of the MUTCD and subject to liability back to the statute of limitations.

    • 0 avatar

      Dear Car Person: YOU seem to know what you are talking about, but I sure don’t. This subject fascinates me, so I like to learn all I can about it.
      May I gently, respectfully, humbly request that you clarify your comment for us regular folk?
      In English?

  • avatar

    They aren’t about safety. Never have been, never will be. If they were, they would immediately lengthen every yellow by 1 second and mandate a 1 to 2 second all red interval. Those two measures alone would drop (and have dropped) accidents by more than 95%.

    Cameras are about $$. That is why most don’t even acrue points.

    Is anyone else surprised you can’t buy discount “red light coupons”, to be used when a camera nabs you?

    • 0 avatar

      That is also because of legal issues. Because the camera captures the car/license plate and not the driver, the ticket goes to the owner of the car–much like a parking ticket or illegal use of a toll road.

      In TX, RLCs don’t issue moving violations; rather, they issue “illegally occupying an intersection,” which is much less severe than “failure to obey a traffic control device.” The fine is lower, and there are not the same insurance/license consequences.

      This protects the rights of car owners–they are still responsible for what happens with their car (just like how you can be sued if your friend is driving your car & gets in an accident), but it doesn’t directly negatively affect them like a cop pulling them over.

  • avatar

    “Only 5 parameters are needed to determine worse case braking; speed limit, road grade, yellow light duration, distance from “stopline” to “in the clear”, and driver reaction time. ”

    I would think there are additional factors to be considered :
    – base road surface,
    – cleanliness and presence of debris like sand, gravel, or material released from base surface due to aging,
    – oil film, drainage patterns,
    – avg vehicle fleet performance,
    – others?

    • 0 avatar

      The ITE formula includes:

      -Reaction time
      -Approach speed
      -Deceleration rate
      -Grade of the approach
      -Vehicle length
      -Intersection width

      The article could have benefited from editing, but the author’s position is sound. There isn’t much reason to set light timing that differs from engineering standards.

      Studies show that compliance rates improve considerably when these standards are followed. On the other hand, camera company contracts have included provisions for the setting of yellow light timing, which would suggest that they have read the same studies and would like to achieve the opposite result.

      These companies profit when we break the law — they collect percentages of the fines that are collected, so more violations = more fines = more revenue for the company. So perversely, these operators have incentives to make sure that we do break the law. This desire for profit is what turns for-profit enforcement into a racket; instead of improving compliance, the enforcers actually want us to fail.

  • avatar

    This is a poor article. It offers no real insight into whether RLCs improve safety. It actually sounds like a random excerpt from a much longer report. For example, I find no explanation of what the author means by “a dangerous tax.” It’s just thrown out there and assumed to be true without support.

    I personally have no problem with RLCs so long as there is sufficient oversight, transparency, and control over them so that basic rights are protected. I do not approve of the specific contracts that cities have entered into because a portion of the collected fines go to the camera companies. Rather, they should be paid for actual work providing, setting up, & maintaining the system. I also disapprove of cities/states not using the revenue for promised purposes. Here in TX, we were promised that funds would go to trauma centers, yet the state issued only one check to our principle hospital through the entire duration of RLC operation.

    I live next to multiple intersections that have/had RLCs, and I’ve driven through them hundreds if not thousands of times. I have witnessed much driver behavior at those intersections. I can say that from what I’ve seen, the yellow lights are fair and safe. (I do not claim that such systems cannot be abused–only that all those around me are not abusive.) Those I know who have gotten tickets admit that they deserved them. I have not yet spoke with any real person (internet rants don’t count) that has gotten one who claims it was unfair/unsafe.

    I have seen quite a bit of research on RLCs, and I do believe the claim that they reduce the rate of severe accidents, such as t-bones, but also increase the rate of minor accidents like rear-enders. I believe the claim that overall injuries and injury severities decrease.

    I also believe that the prime driver of RLCs is money. Safety is just a convenient bonus. I have no problem with that. The fact is that the govt needs money, and they will get that money one way or another. I certainly prefer that those who break the law pay the tax rather than safe, law-abiding people. After all, what you tax you get less of. RLCs–like toll roads and lottos–are thus essentially voluntary taxes, and I choose to not pay them.

  • avatar

    Cameras should be bought, not leased, and the only revenue ATS or Redflex should earn after the sale is technical support or other activities.

    Yellows should be lengthened, yes, but another great feature at intersections are countdown clocks for pedestrians. You see how many seconds are left before the yellow kicks in. That helps a lot (in areas like Wash DC which have them.)

    I think the vast amount of money pulled in is too great a temptation. Once the funds are used for all things great there is no going back. Some areas got caught shortening the yellow and ticketing cars that entered the intersection on yellow in violation of rules. These are multi hundred dollar fines, nothing to laugh at.

    • 0 avatar

      “…Vast amount of money pulled in….”

      If I’m not mistaken, most red light cameras are economic failures. The assumption was that people would keep running red lights. But people adjust. Revenue has fallen off in many areas.

      However, if municipalities are shortening the yellow lights to increase revenue, that is unconscionable. If true, that means local government is willfully putting its public at risk — the polar opposite of the purpose for traffic lights in the first place.

  • avatar

    The way for a city to make money running cameras is to shorten the yellows.

    In California, a new bill – if the Governor signs it – will allow cities to reduce posted speeds by 5 mph, even on streets with a great safety record. That will allow them to shorten yellows, which will increase red light cam ticketing by at least 50%. (Four of the sponsoring cities have red light cams.) Worse, the shortening will increase severe accidents by 30 to 40%. (Source: “Development of Guidelines for Treating Red-Light Running,” Texas Transp. Inst. pg 2-20.)

    AB 529 is on Gov. Brown’s desk for signature – or veto. If you live in California, or visit here, phone him at 916 445-2841, or email him via the form at Ask him to veto. Also phone your union or professional assn. As soon as possible.

    To the supporters of 529: Remember that 529 will increase severe accidents, a lot., just for $$.

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