Why is the Signal Always Red?

 

Why is the Signal Always Red? (Or, the Signal is Always Greener on the Other Side)

We have all experienced the frustration of waiting at red lights for so long they seem broken or the frustration of driving down a street, stopping at every light. This 8-page document takes an informal and interesting look at some of the factors that influence traffic signal timing and coordination. Click on the link to view.

http://www.drcog.org/documents/Why%20Signal%20Red.pdf

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!

I believe a that efficient timing of lights should be a national priority. Los Angeles recently completed their project.
http://www.cbsnews.com/8301-33816_162-57587198/los-angeles-e...

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About a month ago, I was

About a month ago, I was waiting & waiting & waiting at a red light at a busy intersection. More than 10 minutes expired & the lights hadn't changed once. To the credit of those who were negotiating the intersection, they alterenated several cars at a time from each direction to keep the traffic flowing. It was at the exit of a Costco & it spoke well for those shopping there & those locals traversing the light. Nobody even got out of their car to direct traffic. Here, here!!!

I must admit, however, that this kind of problem hasn't happened to me for the past 30 years, so the lights are reliable. The only problem now is that the companies who run the speed & redlight cameras are likely to play with the timing & the County is more than willing to look the other way.

Write your representatives & tell 'em to fix it or it'll me made an election issue. BTW, I don't get tickets of any kind & I do my best not to break laws.

Fred

Likely?

FZbar wrote:

... The only problem now is that the companies who run the speed & redlight cameras are likely to play with the timing & the County is more than willing to look the other way.
...
Fred

Fred, in Tennessee, if it were "likely" that the camera companies "play" with the timing, then I would be among those who would be up in arms and directing my comments to my representatives.

I have not seen any verifiable information that would indicate either ATE companies or political officials have "played" with timings in Tennessee.

Several Tennessee cities (Chattanooga and Nashville) were at one time falsely accused of "shortening" timings.

The National Motorist Association Blog is the origin of the "6 Cities That Were Caught Shortening Yellow Light Times For Profit" myth. The article was posted on March 26, 2009. See http://blog.motorists.org/6-cities-that-were-caught-shorteni...

In a sideline headed "Important note", the blog said "These news stories were collected from the archives of TheNewspaper.com, an excellent resource for anyone interested in traffic laws and other motorist issues."

I have debunked these articles several times in these forums.

"likely" is defined as probable or probably. Surely you are not meaning this!

don't hijack the thread

jgermann wrote:
FZbar wrote:

... The only problem now is that the companies who run the speed & redlight cameras are likely to play with the timing & the County is more than willing to look the other way.
...
Fred

Fred, in Tennessee, if it were "likely" that the camera companies "play" with the timing, then I would be among those who would be up in arms and directing my comments to my representatives.

I have not seen any verifiable information that would indicate either ATE companies or political officials have "played" with timings in Tennessee.

Several Tennessee cities (Chattanooga and Nashville) were at one time falsely accused of "shortening" timings.

The National Motorist Association Blog is the origin of the "6 Cities That Were Caught Shortening Yellow Light Times For Profit" myth. The article was posted on March 26, 2009. See http://blog.motorists.org/6-cities-that-were-caught-shorteni...

In a sideline headed "Important note", the blog said "These news stories were collected from the archives of TheNewspaper.com, an excellent resource for anyone interested in traffic laws and other motorist issues."

I have debunked these articles several times in these forums.

"likely" is defined as probable or probably. Surely you are not meaning this!

This is about some of the issues traffic engineers have in setting the cycle time for the traffic lights in a city especially along a corridor. Take your discussions about shortening timings for profit to your own thread!

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Bigger the road, longer the green.

Most cities have classify roads into different categories. Higher on the classification means longer the green light, and the wait time to turn red is also longer even if no car has passed through. Many people think traveling through smaller roads and streets with less traffic will resulting shorter travel time. But, smaller streets have more pedestrians and cars merge in and out, the possibilities for traffic accidents is higher. That's why traffic engineers want people to stay on the main road as much as possible for easier management.

Sorry

Box Car wrote:

...
This is about some of the issues traffic engineers have in setting the cycle time for the traffic lights in a city especially along a corridor. Take your discussions about shortening timings for profit to your own thread!

Box Car,
if it was a hijack, I apologize but I thought all "timings" were pertinent in "cycle length" - that is, shortening yellows could allow more green. Personally, I favor increasing yellow times but that results in longer reds, if I follow the logic.

I was interested that the link did not attempt to deal with cycles based on the time of day. By this I mean a morning set of cycles as people flow into town to work, and an evening set of cycles as people return home.

I have always been interested in queuing theory and the application to traffic signals. As in many other statistical situations, having good data is a necessity.

After Thanksgiving, I will likely again communicate with our traffic engineer about the need to change the left turn timing of a particular light that lets the South-North traffic enter the mall but backs up the North-South traffic for blocks (not enough capacity). For times other than Thanksgiving and Christmas, the South-North two left turn lanes empty out 4 to 5 seconds before the North-South lanes are given their green (too much capacity for the turn lanes).

What happened is that the major artery was redone to improve traffic flow and the left turn lanes were increased from one to two into the mall. I immediately noticed the backup (in the other direction at the 2 preceding traffic lights) and emailed the traffic engineer about my observations and my feeling that he was trying out how things would work for Thanksgiving. His reply indicated that was what was going on.

the timing is interelated

jgermann wrote:
Box Car wrote:

...
This is about some of the issues traffic engineers have in setting the cycle time for the traffic lights in a city especially along a corridor. Take your discussions about shortening timings for profit to your own thread!

Box Car,
if it was a hijack, I apologize but I thought all "timings" were pertinent in "cycle length" - that is, shortening yellows could allow more green. Personally, I favor increasing yellow times but that results in longer reds, if I follow the logic.

All timings are interrelated, much like the triple constraint in project management. If you shift one element, it shifts all the others as well. This is particularly critical when doing a corridor as the object is to reduce congestion along the primary route while being equitable to any cross streets. Almost all traffic controllers have schedules where the timing for a light can change depending on the time of day. Another fairly recent wrinkle is the adaptive controller that will vary the timings at one intersection based on traffic density. The variations are all subsets of the master time of day settings. What the paper talks about are the challenges faced when trying to handle several intersections to reduce delays.

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help the lights!

I would love the timing of streetlights to be a national priority. The gov't tells us to save gas by checking tire pressure and enacting a law that requires a chip in valve stems.
It appears that properly timed traffic signals would help congestion and save fuel as well.

Only if

grtlake wrote:

I would love the timing of streetlights to be a national priority. The gov't tells us to save gas by checking tire pressure and enacting a law that requires a chip in valve stems.
It appears that properly timed traffic signals would help congestion and save fuel as well.

That could be progress but only if the real intention of the authority/company installing them is for the good of the traffic and not to catch a fine as often as possible.

Red lights

I certainly can not speak to where anyone else lives, but where I do there is buried wiring in the street and when it senses a car sitting there it will change the light.

Unfortunately for law abiding cyclists it does not work too well since there is not enough metal mass.

When I get to an intersection like that I stop and roll back a few feet and go forward again to start the cycle a bit faster.

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Box Car wrote: This 8-page

Box Car wrote:

This 8-page document takes an informal and interesting look at some of the factors that influence traffic signal timing and coordination. Click on the link to view.

http://www.drcog.org/documents/Why%20Signal%20Red.pdf

Interesting.