Shhhhh! The Metro-North quiet car may be here to stay.

The rail’s experiment with specially designated “Q,” or “quiet,” cars will be expanding, Metro-North announced yesterday.

Starting Oct. 17, one car on 36 rush-hour trains on the Hudson and Harlem lines will be for riders seeking a space “free of cellphones, loud conversations and all manner of beeps and buzzes.”

The pilot program on the Port Jervis and Passaic Valley lines will be made permanent.