Why do pedestrian crossing signals count down but the traffic light stays green?

[DaveC426913]

Uh... what do I say now? Do I repeat it, like a dolt?

Why do pedestrian crossing signals count down then the traffic light stays green?

 

[Moonbear]

It might be so the cars have a chance to actually turn at intersections with a lot of pedestrian traffic. I don't live in a place where the crosswalk signs do a count down, and the only place I've seen that is in D.C. and midtown NYC, so I can't be sure, but that seemed to be the situation. Of course, in reality, it doesn't work anyway, because the pedestrians just keep crossing until they see the light change. You'd think it was pointless to bother with a pedestrian crosswalk sign, until you'd been to a place where they didn't exist and realized how stupid the average pedestrian is. Someone forgot to teach a LOT of people, "Cross on the green, not in between."

 

[Jasongreat]

Uh... what do I say now? Do I repeat it, like a dolt?

Why do pedestrian crossing signals count down then the traffic light stays green?

Maybe to give those still wanting to cross an idea of how long they have to cross before the cross traffic is let go.

 

[Pythagorean]

how long does it stay green in your town? It seems like it's up to the traffic engineers, ultimately.

Our delay isn't that long, but I think the point is that people have different walking speeds and if you give them the feeling they have lots of time, the slower people might not make it all the way across. So you have to take the subjectivity of people's time predictions into account.

Even when the lights go yellow then red for cars, the orthogonal lights don't instantly change to green. They delay a bit to give drivers with bad time perception time to get through.

 

[Moonbear]

how long does it stay green in your town? It seems like it's up to the traffic engineers, ultimately.

Our delay isn't that long, but I think the point is that people have different walking speeds and if you give them the feeling they have lots of time, the slower people might not make it all the way across. So you have to take the subjectivity of people's time predictions into account.

Even when the lights go yellow then red for cars, the orthogonal lights don't instantly change to green. They delay a bit to give drivers with bad time perception time to get through.

Likewise for the pedestrians. If they are slow and start across when the countdown has begun, even if they're slow, there's a chance they'll make it across before the light changes. There will always be some idiot who starts crossing as the countdown is on 1...0... and it makes sense to have some lag for them to finish crossing too if the traffic engineers anticipate that there are so many stupid people. Ideally, the light will switch to Don't Walk with enough time for those in the middle of the intersection to get out of the way before the vehicles get the green light to start running them over.

 

[Dickfore]

Does the countdown happen while the traffic light is green, or a blinking red?

 

[Moonbear]

Does the countdown happen while the traffic light is green, or a blinking red?

Are you in Canada? In the US, there's no blinking red. We have green, to yellow (which is very brief, because most people ignore it or accelerate to beat the red), to red. Blinking red and yellow are for intersections where the lights aren't working right. Blinking red should be interpreted as a stop sign, and blinking yellow should be interpreted as a yield sign. Neither is interpreted right by most drivers, and the first collision brings a traffic officer to the scene to direct traffic more appropriately.

 

[D H]

Why do pedestrian crossing signals count down then the traffic light stays green?

You walk 3 to 4.5 miles/hour. Cars, they go 30 to 45. The yellow light is timed for cars, not people.

 

[AlephZero]

The UK using sound warnings. When the road light goes red, a bleeper starts indicating it is safe to cross. After the bleep stops, the road lights flash red for long enough to give pedestrians already on the crossing time to get across, but nobody else is supposed to start crossing. If nobody is on the crossing, it's legal the cars to drive through the flashing red light.

The bleep has the advantage over lights for blind pedestrians (in fact for everybody, since you don't have to look for the light) but it can confuse US tourists. The usual conversation goes something like

"Hey, what does that bleep mean?"
"When it stops, it warns blind people the lights are about to change soon."
"Gee, you mean in the UK blind people are allowed to drive : ?"

 

[Dickfore]

Are you in Canada? In the US, there's no blinking red. We have green, to yellow (which is very brief, because most people ignore it or accelerate to beat the red), to red. Blinking red and yellow are for intersections where the lights aren't working right. Blinking red should be interpreted as a stop sign, and blinking yellow should be interpreted as a yield sign. Neither is interpreted right by most drivers, and the first collision brings a traffic officer to the scene to direct traffic more appropriately.

I was referring to the pedestrian traffic signal.

 

[Evo]

The problem I find with the crosswalk timers here is that they start blinking and the hand to stop comes up before people make it halfway across. I assume this is to discourage people that have not yet started crossing to stay put. Those that started crossing as soon as the go sign appeared are lucky to make it across before the light turns.

 

[jtbell]

Why do pedestrian crossing signals count down then the traffic light stays green?

Around here, the countdown tells you how much time you have left during which you can safely start to cross the street and reach the other side before the cross traffic receives the green signal (and parallel traffic receives the red signal). It's presumably timed for slow walkers; I can still start to cross for a few seconds after the countdown reaches zero, provided that I don't dawdle.

 

[DaveC426913]

I guess I thought this was common. Maybe only in Canada.

Let me clarify what happens.

On a plain old suburban road (in the outskirts of a major metropolis), at an intersection with smaller side roads, there will be traffic lights. These in are very common where I live. A main residential road will have a traffic light every half dozen blocks or so. Despite being a main road, the traffic is not at all heavy except perhaps during rush hour. Few pedestrians are likely to be around.

Main road traffic light is green, pedestrian crosswalk says Walk.

Then, with no one around, the pedestrian crosswalk signal will turn to Don't Walk and begin counting down from about 20. When it reaches 0, it changes back to Walk, and the traffic light stays green (instead of changing to yellow as one would expect in preparation for a stop).

This happens routinely despite the complete absence of cross-traffic or pedestrians.

 

[Containment]

My guess is they put them at intersections where people get hit often so that people feel more safe in crossing that said intersection.

 

[DaveC426913]

My guess is they put them at intersections where people get hit often so that people feel more safe in crossing that said intersection.

No. We have roads that are miles long and have these at every intersection. It is routine.

I can think of one rationale that's marginally plausible. Traffic calming. Seeing signals counting down causes drivers to be more conscious of their speed and of potential cross traffic. With few major crossroads (i.e. no red lights), it is easy to get lulled into a sense that you're literally on a highway and can just whip along these roads at top speed (or more) all the way from start to finish.

 

[D H]

Then, with no one around, the pedestrian crosswalk signal will turn to Don't Walk and begin counting down from about 20. When it reaches 0, it changes back to Walk, and the traffic light stays green (instead of changing to yellow as one would expect in preparation for a stop).

Here the sign changes from Walk, to Walk with a countdown, to Don't Walk.

Your version sound like the person who programmed the light played one round too many of "beer hunter" the night before.

 

[Dickfore]

If it is a pedestrian crosswalk, then a blinking red light means people who are already found on the path can finish their crossing. Other pedestrians are discouraged to start crossing. The countdown shows in what time exactly is left. People who can walk faster can still make it.

 

[DaveC426913]

If it is a pedestrian crosswalk, then a blinking red light means people who are already found on the path can finish their crossing. Other pedestrians are discouraged to start crossing. The countdown shows in what time exactly is left. People who can walk faster can still make it.

Yes yes yes.

Except 'make it' to what? The traffic light stays green. The pedestrian cross walk wasn't counting down to anything.

 

[Dickfore]

Oh, so the pedestrian light shows green, counts down 10 secs, and then stays green again?

 

[DaveC426913]

Oh, so the pedestrian light shows green, counts down 10 secs, and then stays green again?

Yes. Did I not make that clear?

 

[DaveC426913]

1] Typical main residential road traffic light with pedestrian crossing. No cross traffic, no pedestrians. Also just as common in Mississauga though miles of commerical strip mall wastelands and light industrial zones.

2] Light pattern.

 

[D H]

The pedestrian cross walk wasn't counting down to anything.

It should have been counting down to a solid "Don't Walk" signal. Somebody goofed up on programming your city's lights.

Somebody goofed up on the programming in my city, too. Here those countdown timers count down to when the cross traffic will get the green light. This is even dumber than your city's fouled up signals. Would-be race car drivers in my city in their souped up pickups watching the crosswalk countdown rather than cross traffic. When the timer hits zero, they go. Some slow pedestrian is going to get hit.Here's how they work in Lincoln, Nebraska:

I'd argue that even this isn't optimal. Other cities have the countdown while the sign still shows "Walk", and the countdown is to when it switches to "Don't Walk" -- well before the light changes from green to yellow. People walk at about 1/10 driving speed. The intersection needs to be clear of pedestrians by the time the light changes to yellow.

 

[DaveC426913]

Here's how they work in Lincoln, Nebraska:

This is how they work here too.

I don't believe somebody screwed up. It is like this at uncountable intersections and has been so for years.

 

[D H]

This is how they work here too.

Then they are working right.

You are ignoring the ~factor of 10 speed difference of a walking pedestrian versus a car zooming through a yellow light. The walk signal needs to turn to "Don't Walk" well before the traffic signal turns to yellow.

 

[DaveC426913]

Then they are working right.

You are ignoring the ~factor of 10 speed difference of a walking pedestrian versus a car zooming through a yellow light. The walk signal needs to turn to "Don't Walk" well before the traffic signal turns to yellow.

D_H, you are not doing your homework.

The traffic light never changes from green at any point.

The pedestrian crossing signal simply spontaneously (with no cross traffic or pedestrians present) decides to change to Don't Walk and count down. When it reaches zero, it changes back to Walk without the main traffic signal ever changing from green.

 

[Pythagorean]

misprogrammed was the right answer then, I think...

"Never turns red" would have been more helpful :)

 

[D H]

When it reaches zero, it changes back to Walk without the main traffic signal ever changing from green.

That is not the way the signal to which I linked works, and to which you said that that is how your signal works. The signal I linked to switches from "Walk" to flashing "Don't Walk" with a countdown to a solid "Don't Walk". So which is it -- The way the signal to which I linked works, or the way you said?

If the walk signal turns back to "Walk" after the countdown is complete, I would say that somebody messed up programming the signal. That somebody is someone who works for your city's government. I doubt the quality of city-level civil servants varies that much from the US to Canada.

 

[Pythagorean]

I think Dave is talking about the main (car) traffic light not stopping cars for the pedestrians? I.e. the pedestrian programming cycle is still like normal, but it's not synchronized with the car light.

 

[DaveC426913]

That is not the way the signal to which I linked works, and to which you said that that is how your signal works. The signal I linked to switches from "Walk" to flashing "Don't Walk" with a countdown to a solid "Don't Walk". So which is it -- The way the signal to which I linked works, or the way you said?

The details of flashing versus not flashing are not important. Yes, the pedestrian signal flashes while counting down. No biggie.

The issue is with the vehicle traffic light which never changes from green.

 

[DaveC426913]

misprogrammed was the right answer then, I think...

No. Not many, many lights doing this over years. That's no accident.

"Never turns red" would have been more helpful :)

Never changes from green, never changes to yellow, never turns red.

 

[D H]

The issue is with the vehicle traffic light which never changes from green.

The traffic light is for cars going 10 times walking speed. The walk signal is for pedestrians. That order of magnitude difference in speed mandates different signal timings.

Suppose it takes a slow but able person 30 seconds to cross the street but the yellow light lasts all of 5 seconds. The walk signal had better change to "Don't Walk" at least 25 seconds before the traffic signal turns from green to yellow lest that slow but able person become permanently disabled, or worse.

 

[Pythagorean]

The traffic light is for cars going 10 times walking speed. The walk signal is for pedestrians. That order of magnitude difference in speed mandates different signal timings.

Suppose it takes a slow but able person 30 seconds to cross the street but the yellow light lasts all of 5 seconds. The walk signal had better change to "Don't Walk" at least 25 seconds before the traffic signal turns from green to yellow lest that slow but able person become permanently disabled, or worse.

The traffic signal doesn't turn yellow or red ever so the cars are never stopped in the first place.

No. Not many, many lights doing this over years. That's no accident.

So you think they're intentionally trying to get people hit by cars?

 

[DaveC426913]

The walk signal had better change to "Don't Walk" at least 25 seconds before the traffic signal turns from green to yellow

Argh! The traffic signal never changes from green to yellow!
Please stop posting until you have reviewed the thread!

 

[D H]

Then what is wrong with the simple hypothesis that some civil servant messed up?

Does this really need a three page thread?

 

[Jimmy Snyder]

I had to check this out for myself. It was no problem finding a pedestrian timer on a traffic light. In fact there are 3 of them between the nearest bar and my house. That's what makes the trip home so hazardous. Anyway, this time I decided to pay attention to the count down. Here's what I found. The first one didn't work right. As a result, I nearly ran over a little old lady crossing the street. The second one was better. It got to zero just as I was speeding up to get through the yellow in time. Unfortunately, I think I might have dinged a pedestrian that was clearly not paying attention to the numbers. The third one is kind of a blur now as I try to remember just how my car ended up on the sidewalk.

 

[DaveC426913]

It is possible there's one point of ambiguity left.

The pedestrian signals I'm referring to are not pedestrian signals for crossing the main road. They are pedestrian signals for crossing the secondary road, walking parallel with the main road.

 

[DaveC426913]

Then what is wrong with the simple hypothesis that some civil servant messed up?

Does this really need a three page thread?

As I have said about three times now, all the lights behave this way (in more than one city I might add) and it has been this way for years.

A mistake is the least plausible explanation.

 

[DaveC426913]

Does this really need a three page thread?

No! If the participants had read the thread before responding, I would not have had to repeat the scenario multiple times for Pete's sake.

 

[Pythagorean]

No! If the participants had read the thread before responding, I would not have had to repeat the scenario multiple times for Pete's sake.

I think it was a matter of awkward/ambiguous language, but we worked it out (even if it took three pages).

I don't see how somebody could legally or ethically allow themselves to program people to get hit by cars... so I agree with DH, it has to be an error, either in programming the traffic lights or a policy error that forces the traffic engineers to program it this way.

 

[Pythagorean]

wait a minute! I just saw your diagram. You're talking about pedestrian lights that are PARALLEL to the car lights (i was assuming perpendicular.)

This is not an error. The point here is to allow turners to turn. You have to stop pedestrian traffic, even if there's no cross-traffic, so that cars can turn right.

 

[DaveC426913]

wait a minute! I just saw your diagram. You're talking about pedestrian lights that are PARALLEL to the car lights (i was assuming perpendicular.)

This is not an error. The point here is to allow turners to turn. You have to stop pedestrian traffic, even if there's no cross-traffic, so that cars can turn right.

But this is on a long stretch of road with little pedestrian traffic. Why would you need to stop pedestrians? Like every other turn in the world, if there are pedestrians, the driver would simply wait until they've cleared the intersection, then make their turn.

 

[Pythagorean]

But this is on a long stretch of road with little pedestrian traffic. Why would you need to stop pedestrians? Like every other turn in the world, if there are pedestrians, the driver would simply wait until they've cleared the intersection, then make their turn.

hrm, good point. Maybe it's a programming error.

 

[DaveC426913]

hrm, good point. Maybe it's a programming error.

 

[edward]

The problem we have here is that drivers do not wait until the pedestrians have cleared the intersections because the intersections are so congested the drivers don't see the pedestrians. This happens with both right and left vehicle turns.

Here is one of our many intersections with 6 lanes on one street and 4 lanes on the cross street.

On one side of the three lanes in each direction street there are two left turn lanes, three through lanes and a right turn lane.

The streets with two lanes in each direction have one left turn lane two through lanes, one right turn lane and a partridge in a pear tree.

We have no count down lights for pedestrians. They often are stranded on a narrow concrete median in the middle of the street. (if they are lucky)

We call it the pedestrian lottery.

 

[Pythagorean]

That more what I was imagining. Maybe a traffic engineer from a busier area is working on DaveCs block or somebody just used default software, or maybe the pedestrian right of way makes it mandatory policy.

 

[DaveC426913]

a traffic engineer from a busier area is working on DaveCs block

Oh my god don;t make me use the 30pt font.

This is all over the place, both here in my town and all across neighboring Mississauga - city of a half million people.

 

[DaveC426913]

My buddy proposed an explanation.

He suggests that the traffic signal cycle is standard and fixed. So, every two minutes or so, the 'traffic lights are going to go red' sequence begins, and the crosswalk starts counting down to zero - but that the actual test to see if there's any cross traffic does not occur until just before it's about to change. When it does not detect any cross traffic, it aborts the traffic light change.

 

[Containment]

That seems fairly unlikely as dirt covering the sensor that checks for traffic would force a repair person out to fix the lights about every other day. I would bet it's programmed wrong as I believe a few people have said.

 

[Moonbear]

Oh my god don;t make me use the 30pt font.

This is all over the place, both here in my town and all across neighboring Mississauga - city of a half million people.

I think that's the point, that it's a default setting that will work in populated or unpopulated areas. Is there a button to push to cross in the other direction that will change the green light for cars to red? It could be that the pedestrian light in the one direction just keeps running on its timer, and if a vehicle tripped a sensor for the other direction, or someone pushed the button to cross the other way, that's the timing the light would use for cross traffic.

I'm really inclined toward this just being the default setting on the pedestrian lights and nobody bothered changing them because it doesn't matter as long as traffic and pedestians are light, but if there was an increase, they could set them differently later.

There's really no rational explanation for it.

 

[DaveC426913]

That seems fairly unlikely as dirt covering the sensor

The sensors are large metal detecting coils embedded in the road.