another day driving home and hitting all red traffic lights

As the title says I am frustrated with traffic lights and have a question for those out in the ether. My question for this evening is who are these people who program traffic lights, what type of PLCS are used, and finally why does it seem like they are so poorly programmed? My guesses to the final question would probably include incompetence, building in the need for paid return visits, the specs were made wrong (my hope), and lack of funding.

You would think in a world where so many people believe in (what I think is the lie of) human caused global warming they would want to keep cars moving and not have them constantly stop and start.

I am so frustrated that I would be willing to go out and program my cities lights for free.

They don’t use PLC’s they use traffic signal controllers. Last time I had any involvement with them (about 10 years ago now) they were behind the times but the industry was a “good ol boys” club and it was very difficult to instill change. However, change was taking place. Having said that, it is a lot more difficult to do than people think. The number of variables is stunning and something as simple as an un-equal distance between three intersections in a row (A to B =1000’, B to C =750’) can take weeks (sometimes months) to calculate. The difference of 200 cars per hour (going through an intersection) can sometime mean a completely different programming routine. They rely heavily on simulation software that takes feedback to adjust itself so it sometimes takes months for the software to start making accurate predictions. It’s just as much an art as it is a science and again, it’s very hard to get right. I gained a whole new respect for those working in the industry after getting to know some of them and getting a small glimpse of what’s involved (did I mention it’s very hard work?). Using PLC’s would probably be one of the more difficult things to program and would be very hard to justify the time or expense.
http://en.wikipedia.org/wiki/Traffic_light_control_and_coordination
On another note, I’d stay away from political comments. You never know who believes in what (or feels about what) and you run a pretty big risk of ****ing someone off. Just my two cents.

thanks for the response. I googled traffic signal controller and got some interesting information. Included in that information was the fact that my stop light problem is by design. The programmers are trying to change my habits by xxxxing me off (that is to say trying to make me change commute time and route).

Thanks again

I gained a real appreciation for traffic signal control systems while working on the drive system for the busiest bascule drawbridge in the world. I was editing the routines that handle the fallback redundancy and it was a nice, sunny quiet afternoon looking out the door of the control tower across the canal.

Wait... quiet ? Why is it quiet ? The bridge is down and there should be traffic up there.

I climbed up the ladder and looked. At least a half mile of cars. Drivers standing in the middle of the road. A clog of pedestrians looking curiously at the crossing gates, which were not closed despite the fact that all the lights had been red for ten minutes.

Turns out there's a self-monitor circuit; if the bridge controls are in anything but RUN mode, the intersection controllers default to all-stop.

I've never been so thankful for the [Cancel Edits] button in my life.

GlenGineer said:

As the title says I am frustrated with traffic lights and have a question for those out in the ether.

Click to expand...

I just got home and I must have had to stop for every one of the 20 traffic lights between work and home.

First rule of programming traffic lights. Cars going N-S must wait as long as there is no traffic going E-W. Only when a car wants to go E-W will the traffic light stop the E-W car and let the N-S cars move.

The second rules is the same as the first only exchange N-S and E-W.

The traffic light must be able to switch from red to green hold for 3 seconds then switch to yellow then red. I have seen too many 3 second green lights.

Timing between intersections will always screw over most of the cars. If the lights are timed for travelling north the people traveling south will have to stop often.

My question for this evening is who are these people who program traffic lights, what type of PLCS are used, and finally why does it seem like they are so poorly programmed?

Click to expand...

Idiots,
traffic light controllers. I have seen them in the cabinets near the intersection.
what do you expect from idiots?

My guesses to the final question would probably include incompetence, building in the need for paid return visits, the specs were made wrong (my hope), and lack of funding.

Click to expand...

Incompetence and who cares. It is a government job.

You would think in a world where so many people believe in (what I think is the lie of) human caused global warming they would want to keep cars moving and not have them constantly stop and start.

Click to expand...

You think like the rest of us or at least like me. Good for you.

There is a street light near where I live. I while back there was a storm that keep the lights from working. They didn't even blink. Some how there were NO accidents and traffic flowed smoother, less wait time, by just treating the intersection as a 3 way stop. I would have been happy if the removed the lights and just put up stop signs.

I am so frustrated that I would be willing to go out and program my cities lights for free.

Click to expand...

Wait!!!! It is complicated. I wouldn't want to program lights using a PLC. Programming just one intersection using a PLC would not be a problem but to dynamically change the timing for multiple traffic lights to increase flow would not be possible using a PLC.

I am very experienced at implementing optimizing algorithms. These algorithms can't be implemented in a PLC.

@Firejo, are the cables I see running across the road used to collect data for the traffic light controllers? What parameters are used to get the timing right between the lights.

BTW, I would model the cars as a first order plus dead time system with different time constants for acceleration and deceleration.

I live in Vancouver WA, sometimes I drive down the Willlamette valley on I-5. Every once in a while the traffic stops for no reason. In this case there are no traffic lights to blame. It is the stupid drivers.
http://www.wired.com/2009/06/phantom-jams/
I am constantly thinking who is the idiot that has stopped in front of me?

@GlenGineer, you have found one of my sore spots too. People are such idiots.

maybe switching to roundabouts would help...

Ken Roach said:

I gained a real appreciation for traffic signal control systems while working on the drive system for the busiest bascule drawbridge in the world. I was editing the routines that handle the fallback redundancy and it was a nice, sunny quiet afternoon looking out the door of the control tower across the canal.

Wait... quiet ? Why is it quiet ? The bridge is down and there should be traffic up there.

I climbed up the ladder and looked. At least a half mile of cars. Drivers standing in the middle of the road. A clog of pedestrians looking curiously at the crossing gates, which were not closed despite the fact that all the lights had been red for ten minutes.

Turns out there's a self-monitor circuit; if the bridge controls are in anything but RUN mode, the intersection controllers default to all-stop.

I've never been so thankful for the [Cancel Edits] button in my life.

Click to expand...

Hahaha! That's a great story Ken!

Ken Roach said:

I gained a real appreciation for traffic signal control systems while working on the drive system for the busiest bascule drawbridge in the world. I was editing the routines that handle the fallback redundancy and it was a nice, sunny quiet afternoon looking out the door of the control tower across the canal.

Wait... quiet ? Why is it quiet ? The bridge is down and there should be traffic up there.

I climbed up the ladder and looked. At least a half mile of cars. Drivers standing in the middle of the road. A clog of pedestrians looking curiously at the crossing gates, which were not closed despite the fact that all the lights had been red for ten minutes.

Turns out there's a self-monitor circuit; if the bridge controls are in anything but RUN mode, the intersection controllers default to all-stop.

I've never been so thankful for the [Cancel Edits] button in my life.

Click to expand...

Ken although I am on this site to teach and learn specific information about PLCs you have hit on something I like; parables. I had many good professors at university but my favorite was this 75 year old professor who taught some of the basic engineering classes. He had so many stories that have come to mind over the years as I have gotten into similar situations. One of my favorite was: He was given the task of hiring a paving contractor to repave the parking lot. The job was done and seemed right...until the first rain. The contractor hadn't sloped the lot correctly. A big pool of water formed right in front of the main entrance. Everybody had to walk through the pool to get to work. They dubbed it "Lake Hansen" (name changed to protect the guilty). People bothered him so much about it that when the first pot hole appeared in the lot he begged his boss to let him repave the lot.

I don't know why but it seems like the best stories are the ones that involve failure.

skip this post - you don't want to read it ...

I don't know why but it seems like the best stories are the ones that involve failure.

Click to expand...

by the time you've figured that out, you'll be about 68 years old – and you'll wonder why in the heck everybody around you wants to drive so doggone fast ...

honestly, the time that I spend waiting at traffic lights gets applied to the "quiet time" column on my personal clipboard of life ...

but then again, I KNOW that I'm "weird" ... I haven't had a TV set in my house in at least 8 years (even though basic cable is included with my internet connection) ... when I'm staying in a motel out of town I NEVER turn the TV on ... I use a "dumb phone" – and even though I pay for texting as a part of my cell phone package – I call up Sprint (sometimes monthly) and insist that they turn the "texting feature" OFF ... I'm not 100% sure what Tweeting and/or Twitter is – and I've never been to Facebook ... feel free to pity me – but frankly I like my life the way I have it set up ...

I work VERY hard when I do work – but I also know how to "sit loose" whenever I finally get an opportunity to do so ... red lights? ... no problem ... wherever I'm going, they'll wait on me to show up ...

peace ...

My best friend is a traffic "engineer", we get into arguments about this all the time, especially after I drive through his city.

Basically, it boils down to politics and money. Not all intersections are coordinated, those in poorer areas are usually not, regardless of whether or not they are used for commuting. Timing for thoroughfares tends to center around the flow of public transport (buses, trams etc.) in favor of single occupancy cars. In some communities, the coordinated systems are even used to PURPOSELY delay commuters trying to get around regular highway traffic by taking surface streets so they will get frustrated and stop to spend money. That's the case in my friend's town, the decisions were literally made by prominent members of the Chamber of Commerce.

Ken Roach said:

I gained a real appreciation for traffic signal control systems while working on the drive system for the busiest bascule drawbridge in the world.

Click to expand...

Fremont bridge? I used to live near it.

Doesn't your city have the emergency vehicle receivers built into the controllers that give emergency vehicles a green light always when they broadcast the RF signal.

Saw the transmitters for sale to anyone & hesitated for a few seconds before I decided against it.

jraef said:

In some communities, the coordinated systems are even used to PURPOSELY delay commuters trying to get around regular highway traffic by taking surface streets so they will get frustrated and stop to spend money. That's the case in my friend's town, the decisions were literally made by prominent members of the Chamber of Commerce.

Click to expand...

I find that troubling.

It are not Traffic lights, it are Stoplights, and yes the roadowner has a big word in the system used, as he pays the bill he has the privilege to tell the programmers the times.
And yes the incoming lights are always shorter as the outgoing side.
Remeber, when everybody would be a little polite (not politic) you would not need a traffic light.
I would love it when the traffic lights are in yellow when the traffic is low.

Ron Beaufort said:

I work VERY hard when I do work – but I also know how to "sit loose" whenever I finally get an opportunity to do so ... red lights? ... no problem ... wherever I'm going, they'll wait on me to show up ...

Click to expand...

I like your style Ron although I have to say, there aren't too many people who's experience has earned them the right to that "they'll wait on me to show up" philosophy. Out of anyone here, I think you've earned it. I hope to have this attitude as well in another 50 years