An off-duty train conductor got himself into trouble on the rails when he socked a straphanger in the face during a squabble early Saturday, cops said.

Twain Glover, 44, was riding a Manhattan-bound A train near the Hoyt-Schermerhorn station around 2 a.m. when he got into an argument with a 40-year-old woman, cops said.

At one point, he punched the woman — a complete stranger — in the face, police said.

He was taken into custody at the station and charged with assault, cops said.

The woman, who was not seriously injured, was taken to Bellevue Hospital for observation, authorities said.

The subject of the argument was not immediately known.