A quick-thinking commuter saved a teenager who fell on the subway tracks by pushing him down into a trough between the rails, allowing an approaching train to pass right over them, police said.

An 18-year-old man had some kind of medical problem yesterday and fell onto the tracks, which are a few feet below platform level, police said. Wesley Autrey, of Manhattan, saw him fall, jumped down onto the tracks after him and rolled with him into the rut between the rails as a southbound train was coming in.

Mr. Autrey said he initially tried to pull the man up to the platform but had to decide whether he could get him up in time to avoid both of them getting hit.

“I just chose to dive on top of him and pin him down and pin myself down,” he said.

The train’s operator saw someone on the tracks and put the emergency brakes on. Two cars of the train passed over the men — with about 2 inches to spare, Mr. Autrey said — before it came to a stop.

The subway trough, which is used for drainage, is typically about 12 inches deep but can be as shallow as eight or as deep as 24, a New York City Transit spokesman said.

Neither man was hit by the train, police said, and Mr. Autrey, who had his two young daughters traveling with him, refused medical attention. The rescued man, whose name had not been released, was taken to a hospital, where he was in stable condition.

Onlooker Patricia Brown said Mr. Autrey, a Vietnam War veteran, “needs to be recognized as a hero.” Others cheered him and hugged him outside the train station.

The incident took place around 12:45 p.m. at 137th Street and Broadway in Manhattan on the No. 1 subway line.