Cabbies do it from the back of a taxi line at the Port Authority Bus Terminal, coaxing their colleagues to move up a spot. Commuters do it at the mouth of the Holland Tunnel, flabbergasted that others in a city of eight million might share their route.

And should a fellow driver commit the cardinal sin of hesitating at a light just turned green, anyone — from brain surgeons to criminals to the kindliest of grandmothers — can be expected to smack a palm against the steering wheel.

“Those people,” former Mayor Edward I. Koch said, “are the worst.”

Honking.

It is the signature act of the New York City road, and in the grand tradition of jaywalking, it happens to be illegal; everyone does it, but barely anyone is punished.

Now, it appears, the city has effectively thrown up its hands — or, more accurately, taken down its signs.