There are no station announcements to signal to riders which train will arrive first. There are no countdown clocks. And so the travelers help one another, communicating the hints they have trained their senses to capture: the pitch of a screech when a train comes to a halt — unique depending on the line, some insist; the rustling of newspapers, windswept by an oncoming train; the wave of a hand, the nod of a head, a pull on the top of a baseball cap, like a third-base coach advising his player to steal.

“It’s kind of funny,” said Sam Gable, 26, from the Lower East Side. “You don’t really see people help other people in Manhattan very often.”

As with any worthy production, the participants have come to master their roles. On a recent weekday morning, an orderly line formed, stretching from the upstairs M platform, down a flight of stairs to the F, then back up a separate staircase. (Riders say this formation allows word to travel fastest when the proper train arrives.)

Some travelers heard a stirring overhead — an M train, they wondered? No, a young man instructed from the top of the staircase, peering at the platform. Hold your positions.

A breeze wafted up to the turnstiles. An F? Not yet, said a station sage, unmoving. The gust, he said, had not been stiff enough to have come from an F.