The New York Times reports an act that is difficult to explain using traditional rational choice theories.

Mr. Autrey was waiting for the local at 137th Street and Broadway in Upper Manhattan around 12:45 p.m. He was taking his two daughters, Syshe, 4, and Shuqui, 6, home before heading to work.

Nearby, a man collapsed, his body convulsing. Mr. Autrey and two women rushed to help. The man, Cameron Hollopeter, 20, managed to get up, but then stumbled a few steps to the platform edge and fell to the tracks, between the two rails.

The headlights of the No. 1 train appeared.

“I had to make a split decision,” Mr. Autrey said.

So he made one, and leapt.

Mr. Autrey lay on Mr. Hollopeter, pressing him down, his heart pounding. The train’s brakes screeched, but it could not stop in time.

Five cars rolled overhead before the train stopped, passing just inches from Mr. Autrey’s head, smudging his blue knit cap with grease. Mr. Autrey heard onlookers’ screams. “We’re O.K. down here,” he yelled, “but I’ve got two daughters up there. Let them know their father’s O.K.” He heard cries of wonder, and applause.