New York City's placebo buttons and "The Post Hoc Fallacy"




The next time you see a crosswalk button, don't press it.

If you try that in the Seattle area you'll be standing around until either someone else presses it or a car comes up and triggers the light to turn for your direction of travel. Timed intersections that turn for pedestrians anyway don't have buttons. When there's a crosswalk button here, it actually does something.

And yes, I have "done experiments" to prove this.


The real story is that the idea to use placebo buttons for traffic signals was borne out of the successful placebo ballot boxes you guys have had over there for some time now...


Well which do you believe - your so-called "experiments," or a really clever video on the internet? Need I mention the video is endorsed by somebody who's famous on the internet?


I know they don't do anything but I still press them. I just love pressing large buttons.


It may be the case in NYC that they are not wired. I travel a fair bit, and am not willing to say, categorically, that none of them work.

So I have a choice. I can press the button and have it do nothing. The light will change of its own accord and I have given up ... I'm not sure what? If the button is wired, then odds are good that I have just saved myself a lot of time, standing at an intersection, cussing the %$#@ light for not changing.

Seems to me I win either way, since the effort invested in pushing the button is fairly minimal and I am assured that the light will change in all possible instances.


Generalizing from the situation in a busy, pedestrian-oriented city to elsewhere would also be a logical fallacy. In a place like Manhattan or downtown SF, where both heavy traffic and large numbers of pedestrians are expected, the default light cycle already attempts to give both the traffic and pedestrians a turn. But in Silicon Valley there are many crossings where you will never get the "white walking man" if you don't hit the button, and if you just cross when the cars are stopped at a red light you won't make it, because the red light lasts less than ten seconds.

Depending on the situation, a well-designed crosswalk button won't necessarily cause traffic to stop quicker; it may just extend the cycle to allow pedestrians more time. But if there is only a pedestrian crossing and no side street, the cars might never get a red light if you don't hit the button.


The generalization that crosswalk buttons are not hooked up makes me wonder if David McRaney is not as smart as he thinks he is.

I've heard that the "close door" buttons to elevators do nothing as well, according to, "somebody told me that." But I've been in many elevators where they sure seem to work: doors start to close immediately after pressing the button, when there would otherwise be a delay after the last beam-break event.

Behaviors of these systems are not entirely driven by these buttons: they're just inputs to a larger system that may at different times not consider them.

I would love to hear comments from people with first-hand experience: traffic control equipment technicians, please chime in!


If you tried that where I am, you would be waiting forever, as the crosswalk signal is not turned on until you press the button and without it being pressed it is just skipped in the sequence.


Also fun: People have assumed that cities actually intentionally install buttons that aren't connected in order to give people some sense of agency/control over their ability to cross the road. See also elevators and their door-close buttons, which are often disabled so that morons won't keep shutting the doors on other people.


In the Boston area, there are many 4-way crosswalks that don't light at all unless someone presses the button, and I've often had to wait longer because people assume the buttons don't work. The problem with the easy report on "most crosswalk buttons are disconnected" isn't that it's necessarily false, but that it's irresponsible. This video ends by advising people to experiment to find out whether the buttons are connected, but the message that gets to people skimming past the article is "only chumps press crosswalk buttons." Which means they won't press them even when they are connected, and will end up crossing less safely. So a report meant to provide an amusing tidbit about urban infrastructure has the net effect of getting more people to walk into traffic.


i swear I've driven up to intersections where the light doesn't change if your car is in the crosswalk. I had to back up for it to turn green. Am I nuts or is that a thing?


You can see filled-in grooves in the concrete at many intersections, where a coil has been embedded in the asphalt. It's an inductive coil, sensing the presence of a big hunk of metal (read: "car") which may be used as an input. At the last stop light before my office, there's a coil, and sometimes when people don't pull up to the crosswalk, the light doesn't trigger. I've had to wait for a few turns of the light a few times, gently honking (read: "being the asshole") to get the first car to pull up to the proper position to trip the sensor.


The only lesson to learn from this is to be mindful of the post hoc fallacy, but absolutely nothing about crosswalk buttons. Why? Because many crosswalk buttons in NYC are still hooked up, and elsewhere so are many others.

Someone else pointed out the situation with elevator "close door" buttons. The truth is that all elevators, at least in the US, have to have close door buttons. But these only have legally defined functionality when the elevator is in fire service mode (when someone is using the key), in normal operation they don't have to do anything so sometimes they do nothing and sometimes they close the door.


What drives me nuts is when someone presses the button and then crosses without waiting for the light to actually change. Either leave the button alone or ignore the light, don't make it change and hold up traffic for no reason after you've crossed.

Personally, I don't take orders from street lights, and I don't interrupt traffic flow unless it's real busy and a natural gap is not forthcoming. The only two rules of pedestrianism: 1) Don't endanger anyone, including yourself, and 2) Don't inconvenience anyone, except yourself.


This is a bad example of a post hoc fallacy, given that's there is evidence presented before you use the crosswalk button that it will affect the crosswalk signal.


OMG, You have just made a convincing case for Pascals Wager.
No Sarcasm - This is a fair and rational way of approaching that black box, given that it it's not until the light changes that you get to see whether the light changes.

If you get the chance to run the test more than one time on the same corner - we may be able to draw conclusions. .. but assuming we only ever get one go at it in an unknown environment - then the rational choice is to try it anyway.
Nice reasoning!


Personally, I don't take orders from street lights

I've encountered motorists with that attitude...


Spot on. Not every place on earth is just like NYC, which in my opinion is a win-win-situation.

BTW, where I live we don't have 'close door' buttons in elevators, just 'open door' buttons.

That being said, placebo buttons do occur from time to time. 15 years or so ago I was part of a project to build a block of some 300 offices. Every office had a little plastic box on the wall with a dial on it "to control the ventilation system". There was even a neat cable running from the box to the tiled ceiling. While the ventilation system was controlled centrally, but every office inmate (it was that sort of company) hat a little knob to play with. Never had any complaints about the ventilation.


Perhaps the New York city officials just stopped fixing the buttons because they noticed pedestrians there ignore traffic signals anyway.