A 45-year-old man was killed Wednesday night when he rode on top of the 6 train in the Bronx, police said.

Witnesses told police that the man climbed on top of the train and hit an object that caused severe head trauma. He was pronounced dead at the scene.

MTA spokesman Kevin Ortiz said subway surfing is “without a doubt, one of the dumbest things anyone could do.”

The MTA has launched public service safety campaigns over the past few years, including warning about the dangers of subway surfing and skylarking, which is riding on the side of the subway car. There were two reported incidents of subway surfing in 2013, with one fatality.