I have found a traffic light button that actually works when you push it! It is the light at the intersection of Garden Street and Appian Way in Cambridge, Massachusetts. It allows you to cross to the Cambridge Common, near Harvard University. You push it, and and the light immediately goes yellow, then red. Finally, something works as advertised.
Here’s the Straight Dope Classic that’s being referenced.
Do “push to walk” buttons at intersections ever actually work?
Gee, that could lend itself to abuse.
I think most buttons (when pressed) are designed to activate the walk/don’t walk signals and their various timers.
Here’s what I have observed. For intersections that have a timed cycle, pressing a walk button just sets a flag in the program that says, “When the green light comes around in that direction the next time, turn on the pedestrian light as well.” The cycle’s time doesn’t change in any direction at any time.
But for intersections without timed cycles, or during non-busy times when timed cycles are switched to sensor cycles (when the light changes only if it senses cross-traffic), the walk button either initiates the signal cycle to include turning on the walk light, or starts a timer which says, “Wait until something trips the sensor, but if it doesn’t within X seconds, initiate the cycle anyway, and turn on the ped light also.”
Rarely, I have seen some lights that, if the walk button was pressed during a very long green light in the same direction, would turn on the ped light immediately if there was enough time remaining in the cycle for a ped to make it across. It might also extend the total cycle time.
I suspect there are many other options available to the programmers of traffic lights nowadays, since they are all computer-controlled. The sad thing is the programmers probably never have to put up with their own programming as drivers or pedestrians – they just set it and forget it.
In the UK, many pelican crossings (light-controlled pedestrian crossings not at junctions) will change immediately when the button is pressed, if they haven’t been used recently. If you press the button straight after it’s been used, it then waits a set duration before changing. Seems to be a logical solution - ensures that the traffic doesn’t get undue delays, and minimises the delay for pedestrians.
Disclaimer - I work in downtown Albany, NY, USA and have spoken with a few of the public works people about this in passing*. Things may be different in your area.
“On demand” crosswalks only light pedestrian signals when appropriate during the light cycle and when people hit the switch. Crosswalks without switches have a pedestrian crossing time built into the light cycle.
Musicat mostly hit it. The traffic light timing doesn’t really change, because the lights are sequenced to minimize disruptions in traffic flow. What they do with “on demand” crossings is cheat a little time off from vehicular traffic in both directions to allow a brief (extremely brief in Albany) period at the next scheduled direction change to leave all the vehicle lanes on red and light the crosswalks. For instance, at the juction of State and Pearl streets the sequence goes: East/West green and North/South red, North/South green and East/West red, then crosswalks, providing somebody hit the damned button. I’ve almost gotten creamed there a few times, because I always assume that somebody hit the button and it’s safe to cross Pearl when the North/South light goes red. Usually at rush hour that’s a safe assumption, but sometimes it’s not. Incidentally, that’s why you see “No Turns” or “No Turn On Red” signs at urban intersections: the Powers That Be don’t want pedestrians crossing with the signal to get mowed down by impatient right-turning drivers.
The only “odd” signal I have personal experience with is at the crosswalk on Madison Avenue between the Empire State Plaza proper and the State Museum (aka. Rockefeller’s Boondogle). There’s no cross street there, just a crosswalk to allow people to get from one side to the other. It’s an “on demand” signal, and a lot of people (mostly tourists) push the button and expect the signal to change immediately, and then assume that the thing is broken when it doesn’t. It works just fine, it’s just synchronized with the signals at Swan and Eagle, so you may need to wait a few minutes. If nobody pushed a button the traffic light would stay green all the time.
Ultimately, none of this really matters to me, because in this town pedestrians just dash across the street whenever they think they see an opening.
*We were talking about underground utility conduits, and I offhandedly asked why it was that when I hit a geen light they’d all be green, but when I hit a red I could expect to stop at every intersection. I got a long lecture on traffic management (these guys are passionate about their jobs) peppered liberally with asides like “allowing for pedestrians trippng the lights”.
I know of a few “push to walk” buttons in my home town (in Canada) that work as advertised. Some are at intersections, while others are strictly for pedestrian crossings.
The ones at intersections immediately turn the lights yellow, then red for the traffic crossing the crosswalk, while turning the lights green for traffic in the direction of the crossing and illuminating the “walk” sign. When my friends and I were driving, if we happened to stop at a red light at one of these intersections we would get one person to jump out and press the button so we wouldn’t have to wait.
The ones that were not at intersections (just a crosswalk with traffic lights on a piece of straight road) would immediately cause the lights to turn yellow, then red. The lights would never turn red unless the button was pressed. There was a certain amount of time after the lights turned green again that the button wouldn’t work. However, we found that the timing worked out so that we could get a longer and longer line of cars (with angry drivers) as we continued to stand there pressing the button. The crossing right outside of the local “Dairy Queen” was an excellent source of entertainment.
Don’t know if you folks have them south of the border, but we occasionally have buttons at crossings that have a sign above them that says “push for audible signal only”. Many people appear to expect that pushing such a button will still make the signals change faster.
Please explain what the “audible signal” is and what it is for – deaf people, to tell them when the Walk light is on? What kind of sound does it make?
Ergonomically speaking this falls in a category of human/device interfacing that I think needs more attention. If a human presses a button, he has reasonable expectation that something will happen, preferably the thing that is most expected. When nothing does right away, he doesn’t know if the system is inoperative or merely delayed.
For the signal, it would be great if there was some display that said, “walk light will change in X seconds” or something like that.
I have a similar beef with many consumer electronics devices. Press “open” on the DVD player and nothing happens because the open cycle is 20 seconds long and there is no indication that it is working since the display doesn’t say “opening”. But press “open” before the 20 seconds is up, and it begins the “close” mode! Now what – will pressing “open” again open it or close it? The result is 3 or 4 button presses and confusion, when all the display had to do was say, “opening…please wait” (or speed the damn cycle up to open instantly, which is what I really want).
I’ve no idea what the specific audible signal thing is, but in the UK, some crossings have a beeping sound when it’s clear to cross, and those which don’t (or those which shut up at night time) have a buzzer or rotating circular knob underneath the main control box which can be held by someone with sight problems, and activates when it’s clear to cross.
And with our pedestrian crossings, when you press a button and it starts the timer, there’s a “wait” sign above the button which lights up, which indicates that it’s been activated (on both sides of the road).
The only ones I’ve seen in the U.S. say “wait” whenever they don’t say “walk”. What do yours say if not “wait” or “walk”?
According to the NY Times (published 2/27/04) - most of the NY intersections have their buttons disabled. When first installed in the 70’s, they added a small advantage to pedestrians crossing avenues from the less-frequently traveled cross-streets.
However, once traffic increased and the ability for improved technology to manage the increased traffic on the streets, the buttons were disabled - yet the buttons remained without any notice of the change. Thus, these days the vast majority of crosswalk buttons are mechanical placebos (at least in Manhattan)
The link is: http://select.nytimes.com/search/restricted/article?res=F10817FF3A580C748EDDAB0894DC404482
(it requires registration and extra payment)
Mark
Umm… I don’t think deaf people would have much use for an audible signal. 
But, yes, it’s for blind people to tell them when the Walk light is on (but one assumes they wouldn’t be able to read the sign that mentions the audible signal - I never suggested all this was completely logical!). They make a loud chirping or beeping. In some case the particular sound is different depending which Walk light is on (North-South vs. East-West). The button is so that people nearby don’t have to hear the sounds all day.
I think he’s referring to a light by the button itself, not the big one that actually tells people when to cross. I’ve seen ones that say something like wait, and I’ve also seen many that just have an ordinary light that lights up to indicate that the button has been pushed.
OK – I haven’t seen one like that, but it certainly solves the ergonomic problem I mentioned earlier.
Just like elevator buttons that light up when pressed and stay lit until that floor is reached. It doesn’t keep riders from pressing them again, tho, when a door doesn’t seem to be closing or the car moving.
Ah, OK. The ‘wait’ indication is just above the button itself. The walk/don’t walk indication is a green man/red man light, on the far side of the road.
I have an story of an example when a “Push to Walk” button did actually work, although I don’t know if this really counts for anything because I think the signal may have been broken to begin with.
My fiance and I were in his car, and had driven down the end of his street, where there is an intersection with one of the major streets in town. We were planning to turn left, there was another car ahead of us, and the signal was red.
We waited a minute, then another minute, then another. Cars pulled up behind us and the line of cars waiting at the signal started getting really long. When it had been about 4 or 5 minutes, my fiance wanted to try and turn around, but there wasn’t much space to do so, with all the other cars around.
So I had an idea. I got out of the passenger side, ran up to the corner and pressed the “push to walk” button. By the time I got back inside the car, the light had just turned green and we were able to move. This probably doesn’t prove anything, since as I said, the signal seems like it was broken to begin with (the red light has never been that long, either before or since) but I just happened to think of this story when I read the article.
About 15 years ago, I worked 2nd shift in Encino, CA. At night, the intersection of Ventura Bl. and Libbit’s P-T-W button was truly messed up, and the light itself was pretty quirky.
First, if the P-T-W button was pushed at night, generally you could expect a wait of 5 minutes or more(!) before the light would change. Jaywalking was quite common here.
The light wasn’t on an automatic timer - it changed only for traffic on Libbit, or eventually for any poor soul who pushed the P-T-W button. However, the strange part (and the solution for impatient pedestrians) is that every minute, the “Don’t Walk” light would flash along Ventura (the main thoroughfare) and the cycle would continue even to the point of the light turning yellow. Then it would go right back to green with a walk signal again.
This happened all night long regardless of traffic. So the trick was to wait until the bogus light-change cycle started and then press the P-T-W button. The light would then actually change and you could then legally cross the street in a few seconds.
I no longer live or work in So. Cal, and by now they might have put in a system that more approximates sanity there, or not. So you Angelenos may be interested in a SD field trip. 
Having been primarily a pedestrian for the last several years, I’ve got a pretty good idea of how the crossing buttons work in my town. It helps that I used to know one of the city employees whose job it was to maintain the things, and he explained it to me after about the third time I complained to him about a button not working
My city has three major streets. The “main” street is a two-way. There are no buttons at the crosswalks on this street in the downtown area - the walk/don’t walk signs simply change in concert with the the traffic lights 24 hours a day. The other two major streets are one-way streets, with three lanes each. At the intersections with these streets, the buttons are simply disabled during the day - basically from 6:00 AM to some time in the evening. This is to accomodate the morning and evening “rush hour” traffic - to keep it movng. The crosswalk light cycle with the traffic lights, just like on the main street.
At night, the main street lights just keep cycling like they do during the day. The one-way streets, however, give uninterrupted green lights to the traffic on the major streets. This traffic is only stopped by either a car on the cross street triggering the sensors in the pavement, or a pedestrian pushing the button.
There are other crosswalk buttons at a few places in town, and they behave in whatever manner the city decides is appropriate. At some of these intersections, the crossing lights always say “don’t walk”, regardless of which direction traffic is moving, unless a pedestrian presses a button. This is mainly because of the complex patterns involving left-turn-only lanes in all four directions. The light pattern doesn’t have to account for the walk signal unless it’s needed. One crosswalk in particular happens to be at the very first traffic light at the south end of the main street. That traffic light is always green, probably to accomodate the traffic coming off the bridge at the south end of town. They don’t want traffic backing up onto the bridge, obviously. So that light only turns red if there is cross traffic or a pedestrian presses the button, even during the daytime.
In my neighborhood, these rapidly insert a “walk” signal into the cycle in a school zone or at an intersection with left-turn signals that otherwise guarantee a steady flow of traffic across the walkway.