What's the Right Way to Program Stoplights?

I'm not a student, just a traveler who gets tired of sitting at a red light when there's no other traffic.

We often see questions on this forum from students asking for advice on how to program traffic lights. My question is what is the sequence supposed to be for a "smart" traffic light (one that uses sensors or cameras) to control the intersection's traffic?

Is one road always dominant?
What type of sensors are in the road---huge prox switches, weigh scales, etc?

Answer: so that I get to go first!

Sensors are usually inductive loops in the road or cameras or other similar stuff.

For sequencing, it can depend on time of day or traffic flow patterns. It may be to prioritise the traffic into town at 8-9 am but out of town at 5-6pm for example.

City wide traffic flow is a science in itself, with a lot of lights programmed so you get stuck at the next set if you go slightly over the speed limit

I have a theory that most lights are not really set up by anyone that actually knows what they are doing - or cares. I know there are some decent systems out there that coordinate traffic pattern times and try to manage prioritize depending on expected needs. I also have to assume that controlling traffic is harder than it seems (well I hope so). It has always seemed to me that some of the flow control algorithms would work to better control traffic flow. Maybe I am naive. I also would expect that with the new camera systems, one would be able to set them up for different optimizations depending on the communities needs. One setup may just optimize traffic flow. Another might optimize for energy savings - dont stop moving traffic or large vehicles unless necessary. The environmentalists could have a blast with that one.

I guess I have spent way too much time sitting at lights thinking about this.

Russell

There is one system, I beleive it is called "green wave", that tries to time traffic lights along a major road in such a way that once you start on green and keep moving at the recommended speed (signs posted), you will most likely keep hitting green all the way along. I don't know is it just based on timing or is there some kind of central controller involved (which means there has to be some communication means to each traffic light).

Of course, even with this system, one still has to decide what to do at the intersection of two major roads. And, of course, I see too many towns and villages installing traffic lights at very short distances (a block or two) so traffic at rush hour can never releive.

What I want a solution to is
1. The checkout counter line I am in ALWAYS moves slowest
2. The freeway lane I am in ALWAYS moves the slowest
3. Bills travel at speed of light where as payments are like molasses in the Antartic.

Dan Bentler

Wouldn't it be nice if there was a member of this forum as knowledgable about traffic control as Dick DV is about drives.

There was a local radio station that as a prank, on-air had a segment about how all the city lights were retrofitted with audio sensors so that if you honked your horn three times, the light would change for you. Many people bought into it at face value and all the honking caused quite the confusion. I think the station got into a bit of trouble over that one.

The idea of the "green wave" concept will work just fine, but only in one direction. If you synchronize the lights so that eastbound (for example) traffic hits all the lights green over a 3 mile stretch by driving the speed limit, the WESTbound traffic will suffer the consequences by having to stop MORE often than if all the lights were just "in sync".

The small town I grew up in actually split main street into two one-way streets a block apart so they could "green wave" BOTH east and west bound traffic. Fortunately north and south bound traffic were both very light in this case.

MY pet peeve NOW is watching the road department double the right turn lane so there are two, time after time, at GREAT expense and GREAT inconvenience during the construction, and then putting up fresh new "No Turn On Red" signs when they are done.

I don't know if the highway department is open to suggestions, but I'd be willing to bet the combined talent available on this forum could CERTAINLY come up with some.

Stationmaster

leitmotif said:

What I want a solution to is
1. The checkout counter line I am in ALWAYS moves slowest
2. The freeway lane I am in ALWAYS moves the slowest
3. Bills travel at speed of light where as payments are like molasses in the Antartic.

Dan Bentler

Click to expand...

Sounds like you just need to slow down!

dogleg43 said:

I'm not a student, just a traveler who gets tired of sitting at a red light when there's no other traffic.

We often see questions on this forum from students asking for advice on how to program traffic lights. My question is what is the sequence supposed to be for a "smart" traffic light (one that uses sensors or cameras) to control the intersection's traffic?

Click to expand...

One more thing. The large number of variables regarding traffic light systems is what makes them such great assignments for the students that come here for help. It gives US a great opportunity to admonish them to carefully define EXACTLY what they are trying to accomplish. THAT step is THE most important step in successfully building what the customer wants, the eventual goal of these students once they get out into the real world. It's not as simple as saying "I'm making a traffic light".

Stationmaster

I live in Perth: the small (and only) city on the West Coast of Australia.
Prior to becoming a private contractor, my old employer spent much of his working life as an Electrician for the Main Roads Department (who deal with traffic lights, etc). From him, I learned that the "tuning" of traffic light systems is something of a Black Art.
As can be seen from other posts on this subject, the programming of an intersection is not as straightforward as it may seem at first.
Often, the behaviour of a given intersection (or set of intersections) can be improved substantially by very subtle changes to the various parameters. For example, a change of just +/- one second to the timer/counter loop which monitors vehical frequency through the intersection can make a very large difference in some cirumstances.
Of course, this tuning requires carefull observation of traffic flow over a prolonged period and a very good understanding of the driving habits peculiar to the population of a particular city.
My boss frequently noted that when the city went to a private contractor to maintain the traffic light network, this skill set was substantially lost and this type of preventative maintainence virtually ceased.
It seems that as with any other complex system, you can get a good, reliable, efficient network - but it requires constant maintainance and "tweeking" to maintain that efficiency.
What city would pay for that these days?

The only requirement to time lights is the ability to say to the press "We need more money". Nothing else maters, and no one is ever held accountable.

In Oakland County Michigan, they are going to spend a million dollars putting a chirping light at a round-about so a blind guy can wander in traffic.

Mark_H said:

The only requirement to time lights is the ability to say to the press "We need more money". Nothing else maters, and no one is ever held accountable.

In Oakland County Michigan, they are going to spend a million dollars putting a chirping light at a round-about so a blind guy can wander in traffic.

Click to expand...

I thought the idea of a round-about was so that you wouldn't NEED a light.....

Latest version of student study traffic lites. Here in Seattle area state Dept Transport is gonna put signs with variable speed limit set for congestion, construction, snow, ice. On I 5 they are going to mark lanes with X to indicate those that are closed ahead.

OK now let me start another argument. On uncontrolled traffic circles do you circle right or circle left? Hmmm sounds like a sqare dance call. Where and when do you do the dosey do??

Dan Bentler