You press a button three times and it is wired to nothing

Three presses in and the light is still red. You press again, harder, with a knuckle, and glance sideways in case anyone saw you. And everybody does it, and in more places than you think that button is not wired to anything.

The best-documented case is New York. In February 2004 The New York Times published the city transport department's own figures: of the 3,250 pedestrian buttons installed on the streets, around 2,500 were deactivated. About 750 still worked. It was not a fault or an oversight. From the 1970s onward the city moved its signals onto central computer control, on fixed cycles that admit no interruptions, and the buttons stopped mattering. Ripping them out would have cost around a million dollars, so they stayed where they were, little sign and all.

The same goes for lifts. In the United States, the 1990 accessibility law requires doors to stay open for a minimum time so that someone moving slowly can get in. The result: in a great many lifts installed since then, the door-close button pays no attention to an ordinary passenger. With the service key it works. For firefighters, it works. For you, no.

Engineers have a name for this and they do not hide it: placebo button. And the reason for leaving them in place is not only what removal costs. It is that waiting while pressing feels shorter than waiting still. The traffic light cycle has no idea your finger exists: it lasts the same number of seconds as if you stood still.

Before you take against every button in your neighbourhood: in Spain and across much of Europe plenty of them genuinely rule, above all outside the centre, at night and at low-traffic junctions, where the light stays green for cars until somebody asks to cross. And the ones with a small speaker or a raised pattern underneath are almost always the real thing, because as well as calling the phase they trigger the audible signal for blind pedestrians. Press that one even in a hurry, and not for your own sake.

There is a way to settle it at your own crossing and it takes two days. Tomorrow, time it from the moment you reach the kerb until the light turns, touching nothing. The day after, same crossing, same hour, press the moment you arrive. If the number comes out the same both times, yours is decorative. If it drops, congratulations: yours rules, and the twelve neighbours who were waiting with you owe it to you.