Knoxville Red Light Camara’s
WBIR has a story (here) about the first ten intersections that are LIKELY (the list is not 100%) yet to get red light cameras. They are all bad intersections so whatever.
My issue with these things are still two fold though.
#1) - The company that is running them has a string of enforcement (false tickets, rigged cameras) issues in their past and they get paid weather the ticket is just or not (i.e. for just mailing it). Knoxville is and was stupid to get into bed with this these people. Lie down with dogs, get up with fleas.
#2) - Until Knoxville institutes a standard and consistent 5 second yellow light (which will has been shown to reduce accidents SIGNIFICANTLY) then I am and will be convinced that this is more about money then about safety. Five second yellows would be INCREDIBLE!! I personally timed the yellow lights I see every AM and PM going to work and it was around 3 to 3 1/2 seconds consistently at various locations.
So, KPD, Knoxville / Knox county government, etc….BOO!!! Not because the cameras are invasions of privacy (you are in public you can not expect privacy in public), nor because they could be used for speed enforcement (which at this time they are not and we will cross that bridge when / if it happens), but because you are working with a bad company and you are not taking simple safety steps (yellow light timing) as well.
Let me preface my comments below be mentioning the fact that yellow intervals are to notify motorists of an impending change and for the clearance of an intersection. They are not an extension of the green phase, even though that is how they are viewed by motorists. (Nerdy talk, I know, but I am a Transportation Engineer)
Please allow me to toss in my 2 abe lincolns in on this post:
#1) I can see your point here, maybe these guys aren’t the best way to go. However, we all know decisions are made with other circumstances in mind…
#2)Where do you find that 5 seconds is a standard and safer interval time? Why would 5 seconds be incredible? So you would have more time to squeak through the intersection on your commute? Longer yellow intervals tend to increase driver disrespect. Yellow times are calculated in one of two ways:
1. Kinematic model: This formula was developed by the Institute of Transportation Engineers and takes into account factors such as: driver perception/reaction time, intersection approach speed, grade of road approach, and a comfortable deceleration rate.
2. Rule of Thumb: Something to this effect:
• If speed is less than 35 miles per hour
(mph), a yellow time of 3 sec. is used.
• If speed is between 35 mph and 50
mph, a yellow time of 4 sec. is used.
• If speed is greater than 50 mph, a
yellow time of 5 sec. is used.
Both of these methods allow longer times for higher speeds. A five second yellow time is not feasible for all approaches. Another point I would like to bring up is that you timed the yellow phases for some intersections you encountered. However, did you all account for the all-red phase? This phase is also part of the clearance time and insures conflicting traffic does not immediately enter the intersection. Your yellow time may have only been 3.5 seconds, but if you had a all-red phase of 1.5 seconds, then guess what- you have the five second clearance you are seeking.
Comment by
James Norris — 3/7/2006 @ 4:19 pm
First of all thanks for commenting and adding to the discussion. Your comments are very interesting and informative. Great stuff. I particularly enjoyed learning about the models that are used in determining length of yellow, etc.
With that said, this is not my first post on this subject, but I will repeat a bit of what I have said before on the topic first.
First of all, I have never thought of the yellow as a extension of the green. I know and use the yellow as a warning. I may be rare, but that is the truth. I have personally never gotten a ticket for running a red, and though I get honked at A LOT I stop on yellows unless I am already over the white line or in the intersection, so this system is unlikely to personally impact me.
Basically, I do not want to see yellow lights longer where more people can get through, but where people can clear intersections safely. It drives me crazy for three or four extra cars to go through a red light, but when the car clears the white line on or at the time of a yellow it should have time to clear the intersection before the red appears, and that does not always happen. Thus my issue with the timing of yellow lights in Knoxville.
I have personally witnessed many times when the yellow is not long enough for a vehicle to clear the intersection without the red appearing. It is just as dangerous from my view for a car to break and stop mid intersection (across the white line) as for people to take advantage of the yellow (and some of the red) to continue through.
As for your two approaches, I am not sure which one Knoxville uses, but either way Knoxville could use a longer yellow. Again I have no problem enforcing the law on red lights, but when the light goes from green, to yellow, to red before a car that is a few feet from the white line when the light change begins I know the yellow is too short - regardless of the speed.
I have personally witnessed just that numerous times in Knoxville. IF the car had braked at the sign of the yellow it would have stopped on the other side of the intersection and probably causing a wreck in the process. Basically, I do not think - based on personal observation of Knoxville traffic of almost 20 years - that the models used in Knoxville properly account for reaction time and speed - which leads me back to thinking Knoxville is not following the models - either of them.
Simply I do not think Knoxville is as worried about safety as getting ticket revenues because they have not taken steps to try to ensure additional safety, be it via longer yellows or greater enforcement of red light violations. I am equally bothered by the idea of “5 more on red” violators, as I am the city not having proper yellow lengths.
As for the five second yellow standard. That came from several different stories, studies, and posts that I have read across the web (some by traffic people, some by motoring groups, some on government sites, some from university studies, etc) that seems to consistently point to 5 seconds as being a reasonable yellow light time that when implemented reduces accidents.
As for the all red phase, that is true - regarding the extra 1.5 seconds, but what I am going on is the fact that a car that is near the white line of the intersection would see yellow, then red before it could clear - thus getting a ticket via camera because the light went red. If the camera did not take the picture until after 1.5 seconds of red that is a different story, but as I have read and understand the system to be, it begins taking pictures on red in the direction of the oncoming not after a 1.5 second delay - when the red goes to green in other directions. So, though the 3.5 seconds of yellow + 1.5 seconds of delay before green in other directions does equal 5 seconds it is not a 5 second legal yellow if the camera starts shooting after 3.5 seconds in the oncoming direction. My concern is still that the set length of time - i.e 3 or 3.5 seconds - is not sufficient for a car that is at the intersection at the time of change to clear without getting a ticket. That concern is what points me back to seeing this as a money maker before a safety device in the eyes of Knoxville government.
I would have NO issue with cameras if I could personally see Knoxville trying to make their intersections safer by other means as well and if Knoxville had gone with a company that had a track record of fairness. My issue with this project lies in the lack of other steps (yellow light consistency, enforcement, etc) that Knoxville has taken before going to this. This was virtually a non issue for the KPD, Knoxville engineering, the Knox County sheriff, Knoxville / Knox County governments, etc until they saw dollar signs. That fact is what leads me to be wary of the sudden interest. The fact that they chose a company that is high in collections and low in consistency just reinforces that to me.
Again though, thanks for sharing, commenting and your information is / was interesting. I think on this one though we may just have to agree to disagree, which is the great thing about a free nation.
Comment by
admin — 3/7/2006 @ 5:36 pm