They learn ’em early these days.

Seen and overheard on the crosstown M86 articulated bus: A mother, early 30s, and her son, around five years old, sitting in seats halfway back, where the bus articulates.

The bus pulls over at Second Avenue.

Mother: Okay, this is our stop, time to get off.

Son: We go out the back, right?

Mother: Yes, we do.

Son: Because the back door is closer.

Mother: Right.

They proceed to the rear exit, which is closed. Instinctively the five-year-old bellows, “Back door!” to the driver up front.

Mother and son disembark to the amusement of their fellow passengers.