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Title: Cities Shortening Yellow Traffic Lights for Profit Post by: patric on May 21, 2008, 09:05:59 pm http://www.motorists.org/blog/red-light-cameras/6-cities-that-were-caught-shortening-yellow-light-times-for-profit
Does this sound familiar? And now even TPD is on record wanting synchronized signals in Tulsa: http://www.fox23.com/news/local/story.aspx?content_id=dcbd32ed-86b3-4399-9fc6-26caa7c0c017 Wow, they must have found another revenue source [:o)] Title: Cities Shortening Yellow Traffic Lights for Profit Post by: TURobY on May 22, 2008, 05:11:24 am How does them increasing the amount of time that the intersection is clear have anything to do with the shortening of yellow lights in six other cities?
Title: Cities Shortening Yellow Traffic Lights for Profit Post by: Wilbur on May 22, 2008, 05:57:56 am quote: DITTO! Nor does Tulsa use red light cameras. Title: Cities Shortening Yellow Traffic Lights for Profit Post by: Hoss on May 22, 2008, 06:57:24 am quote: Yet..... Title: Cities Shortening Yellow Traffic Lights for Profit Post by: patric on May 22, 2008, 09:53:36 am Tulsa has yellow-light intervals shorter than the national average, even though it is not on that list. It appears local newspapers or TV reports are the ones bringing this to light, with the collection of traffic revenue at the heart of the problem.
The FOX23 story on timing lights only mentioned adjusting the red intervals so that they overlapped (without mentioning that the yellow intervals were too short, another known traffic problem). They need to follow up. If the engineers are there with their heads in the boxes adjusting the red intervals, the same effort could be made to correct the deficient yellow intervals, but their reason for not doing so may not be based on legitimate traffic engineering needs. State law says operators, not vehicles, commit traffic infractions, so you have to issue tickets to drivers and not cars. Its the reason we havent been sucked into the red-light camera scams plaguing other parts of the country. How that's exceptioned to allow Pikepass automated ticketing and parking tickets issued to vehicles I just dont know. That's just as good we dont have red-light cameras, because a lot of cities have had to spend more money removing them because they have actually been known to increase accidents, and many have just flat become unprofitable. Title: Cities Shortening Yellow Traffic Lights for Profit Post by: Wilbur on May 22, 2008, 04:42:42 pm quote: Please, tell us how long Tulsa's yellow light intervals are and then tell us your source. Title: Cities Shortening Yellow Traffic Lights for Profit Post by: Chicken Little on May 22, 2008, 05:03:11 pm Point of order, please. "Sychronized signals" is something else. It's not the duration of an individual red or green light, nor is it the pause between switching.
Synchronized signalling is the coordination of a series of lights so that traffic moves at a slow steady pace and doesn't get stuck idling at lights. It's like we have downtown on Cincinnati and Detroit; if you drive 17 miles an hour you'll hit every light. I think this is an important distinction because what Patric is talking about sounds like a bad thing. But signal synchronization where it has happened, has reduced drive times and helped get places back on the air attainment list, which sounds like a good thing. Outside of downtown, our signals are not synchronized, I'm pretty certain. Title: Cities Shortening Yellow Traffic Lights for Profit Post by: joiei on May 22, 2008, 05:21:49 pm I think I have found the source (http://"http://www.motorists.org/blog/red-light-cameras/6-cities-that-were-caught-shortening-yellow-light-times-for-profit/") of patric's warnings. Now, patric, go to some intersections and do some timing and come back and report to us. Are the yellow lights 4 seconds or 3 seconds or something different. I have noticed short greens but never short yellows.
Title: Cities Shortening Yellow Traffic Lights for Profit Post by: nathanm on May 22, 2008, 06:46:36 pm quote: And equally important, but often forgotten, what is the 85th percentile speed of freely flowing traffic on the given road? That's what yellow light timing should be based upon. Title: Cities Shortening Yellow Traffic Lights for Profit Post by: patric on May 22, 2008, 11:03:04 pm quote: That does look a lot like the URL I cited at the top of the thread. Im also surprised a Tulsa cop would not know the yellow light interval of his own town, but I guess Im as capable of using a video camera to document it as anybody. As for other cities, California mandates a minimum of 4.3 seconds, http://www.thenewspaper.com/news/06/670.asp Denver is switching to 4.3 seconds (or more) to reduce collisions, http://www.rockymountainnews.com/news/2008/mar/29/city-may-yield-to-longer-yellow-lights/ Chattanooga, TN is 3.9 seconds, http://www.thenewspaper.com/news/22/2269.asp Dallas is 3.5 to 4 seconds, http://www.thenewspaper.com/rlc/docs/2007/kdfw-rlcdallas.pdf Washington DC is 4 seconds, and so on. Some quick searches turn up some background on traffic light timing: Historically, amber times have been set between three and six seconds, depending on a host of variables from the posted speed at an intersection to the grade of its approach. The formula for these standards comes from a hodgepodge of recommendations by the Institute of Transportation Engineers (ITE) and the Federal Highway Administration's "Manual on Traffic Control Devices." To give just an inkling of how things have changed over the years, in the mid '70s, the Institute of Transportation Engineers recommended a yellow time long enough to factor in reaction time plus stopping time plus "clearance time," or the time it takes to get through an intersection. But by the late '90s, that standard had been steadily eroded by altogether shaving off clearance time, lowering yellow light intervals by as much as a third, which often leaves the motorist stranded in the dilemma zone. To make matters worse, the ITE, which in 1985 was still recommending yellow lights be lengthened to help clear intersections, now, with the advent of red light cameras, offers that "enforcement can be used instead." The real-world translation here is that according to 1976 practices, an 80-foot-wide intersection with a 35 mph approach on a 2.6 percent downhill grade would warrant a five-second yellow light interval. But according to 1999 formulas, it is considered acceptable to allot the same intersection a 4 second interval. Title: Cities Shortening Yellow Traffic Lights for Profit Post by: sauerkraut on May 23, 2008, 08:02:18 am I think many reds are too long on the main Tulsa drags, and arrows for left turns when no cars are there making a left turn is bad and senseless. Remember, no matter what kind of old heap you tool around in, a idling engine always gets zero miles per gallon and pollutes more... Arlington, Texas did something great back in the mid-1980's that they called "things that go blink in the night"- They made many of the traffic lights all flashers in the wee hours of the morn. It improved traffic flow alot for night shift workers. I don't know if they still have that program or not. None the less many more traffic lights in Tulsa can be blinkers over night.
Title: Cities Shortening Yellow Traffic Lights for Profit Post by: Wilbur on May 23, 2008, 08:32:52 am quote: There is no ordinance that mandates the length of a yellow light and that length is determined by traffic engineers, not police officers. I'm simply asking for proof of the comment quote:. Please tell us what the national average is (please don't quote just three or four different cities), then tell us what Tulsa's is. I may agree with you (but doubt it). Title: Cities Shortening Yellow Traffic Lights for Profit Post by: patric on May 23, 2008, 01:00:07 pm quote: I never stated that yellow light intervals were determined by police officers, that was your inference. However, I would be somewhat shocked if any effort to either reduce yellow light intervals for the purpose of increasing citations, modify red-light intervals or synchronizing lights for better traffic flow was done without consultation with the department that ultimately has to deal with the outcome (being the PD). Title: Cities Shortening Yellow Traffic Lights for Profit Post by: BKDotCom on May 23, 2008, 01:26:12 pm quote:Cincinnati is no longer sync'd. Supposedly 71st west of Memorial is sync'd. Title: Cities Shortening Yellow Traffic Lights for Profit Post by: PonderInc on May 23, 2008, 03:57:58 pm Downtown needs sensors, not synchronized lights. Nothing worse than trying to traverse downtown "against the lights" late at night. (Though it IS fun if you can "catch the wave.")
I have a question about the camera-looking-thingies that I'm seeing all over town. Are those cameras for discouraging running red lights? Or are they sensors to detect traffic at the intersections? Title: Cities Shortening Yellow Traffic Lights for Profit Post by: PonderInc on May 23, 2008, 04:05:11 pm When I lived in Colorado Springs in the early nineties, there was a huge gap (like 3 seconds) between when one direction turned red and the other direction turned green. As a result, the unstated rule was: "3 cars go through on red." If you didn't go, people would honk at you!
When I came back to Tulsa, I almost got killed b/c I was still expecting to cruise through the "young" red lights. It was a big shock to discover that the other people already had a green! Title: Cities Shortening Yellow Traffic Lights for Profit Post by: mrhaskellok on May 23, 2008, 04:19:50 pm I am not an expert, but I think they are strobe sensors...for the Fire trucks...if you look at a fire truck head on while it is running code you will see a strobe light flashing above the windshield...that strobe is flashing at a precise frequency. They then mount a camera like sensor that detects only that frequency. The camera, when "activated" turns all the lights red except for the direction the fire truck is headed...ideally this clears intersections several seconds before the fire truck arrives.
Title: Cities Shortening Yellow Traffic Lights for Profit Post by: Wilbur on May 23, 2008, 06:42:49 pm quote: Consider yourself shocked! Tulsa has traffic engineers who go to school for years and years to be trained in traffic engineering issues and traffic flow. I'm confident Tulsa follows federal ANSI guidelines for signage, speed limits, road markings, ......... I'm also confident yellow and red lights are part of those standards. As for synchronizing traffic signals, that is a luxury Tulsa would love to have, but is also extremely expensive. It requires all of the signals be able to talk with each other, which they currently can not do. Except for downtown, and a few intersections where traffic signals are close to each other, say on either side of I-44, and the one experimental synching happening on 71st Street around Memorial (paid for with a grant?), no other lights are currently synched, nor do they have the ability to without upgrades. Title: Cities Shortening Yellow Traffic Lights for Profit Post by: patric on May 23, 2008, 06:45:04 pm quote: The latter. They are "machine eyes" to detect vehicles, replacing the loop of wire that had been embedded in the concrete as motion detectors. They look like cameras 'cause they are. Sgrizzle gets credit for that find. Red-light cameras are still illegal in Oklahoma. The sensors that preempt traffic signals to let emergency vehicles through are a whole different system, they look like this: (http://upload.wikimedia.org/wikipedia/commons/thumb/7/73/Millersville_opticom.jpg/800px-Millersville_opticom.jpg) Title: Cities Shortening Yellow Traffic Lights for Profit Post by: patric on May 23, 2008, 07:02:16 pm quote: Maybe, maybe not. If Tulsa were following ANSI guidelines for street illumination we would be using full-cutoff (low glare) fixtures (per ANSI/IESNA RP-8-00 (http://"http://webstore.ansi.org/RecordDetail.aspx?sku=ANSI%2fIESNA+RP-8-00")). Im stunned that individual police officers arent behind such a standard. If you visited a city that used Full-cutoff streetlighting you would be amazed at how much better (and further) you can see on the street. Title: Cities Shortening Yellow Traffic Lights for Profit Post by: mrhaskellok on May 24, 2008, 12:11:39 pm I don't think officers, or any other majority of a workforce, thinks about stuff like that. This is why I dislike the concept of 9-5s. Your work and work load should be performance and result oriented. We should pay our officers more if crime goes down and less if crime goes up...this incentivizes them to get involved in things like street lighting and such.
Title: Cities Shortening Yellow Traffic Lights for Profit Post by: Hawkins on May 24, 2008, 08:56:19 pm Only in a place like Tulsa would this even be a point of discussion.
In large cities, like Dallas, the yellow light means nothing, the red means, only three or four more cars can pass. [}:)] Title: Cities Shortening Yellow Traffic Lights for Profit Post by: si_uk_lon_ok on May 26, 2008, 02:21:48 pm quote: Just to say that while synchronising traffic lights is expensive, the extra capacity it provides can usually outweigh the costs if the road is at or reaching capacity. It also needs detectors to run a smart system that doesn’t trap you with the normal sequencing at 3am. The move to cameras overhead rather than inductive loops buried in the ground is largely due to reliability and cost. The technology has improved the quality of IR or microwave radar systems which usually are more reliable and don’t involve digging up the road to fit and replace. The loops also run into problems if the road is very wide. |