The young man leaped onto the tracks just as the downtown A express entered the West 4th Street station yesterday morning. The train screeched to a violent halt. The operator watched helplessly.

“He saw me come in and I grabbed the brake and he lay down,” the train operator, visibly shaken, told his supervisor just after 10:30 a.m.

“He jumped, though?” the supervisor asked.

“Yeah.”

The medical examiner has not officially ruled the incident a suicide, but police said they don’t suspect any criminality. The identity of the victim was not immediately released.

Yesterday morning’s fatality was the 22nd time this year a train has struck and killed someone, a number on a par with the rate in 2004, when 41 people died under subway cars, according to police figures.

At the West 4th Street station, police could find no witnesses, though people evacuated from the train knew immediately that something was wrong. The train stopped with enough force to send riders scooting off the train’s plastic benches. Cars at the rear heeled at a worrisome angle. The conductor announced a mechanical problem, belying the true cause of the one-hour delay.

“You knew it wasn’t good news,” one passenger, Vivienne Papadatos, said after the train was evacuated. “The train stopped way too quick.”

The platform quickly grew crowded as wide-eyed onlookers craned their necks. Grim-faced police officers and firemen worked to remove the body from underneath the second car of the train.

Except for the occasional roar of local trains, the platform was unusually quiet. “I can barely talk about it,” another passenger, Rosie Blitchington, said.

Another rider, Richard Martinez, crossed the station immediately to the uptown platform. There, he said he had seen a young white man with close-cropped blond hair under the tracks. The victim appeared to be about 17, Mr. Martinez said.

“To me, that’s a baby,” Mr. Martinez, 37, who has two teenage children, said. In 2003, in the five boroughs, 484 people committed suicide, most by hanging, strangulation, suffocation, or jumping from a high place, according to the city’s Bureau of Vital Statistics. Twenty-four people committed suicide by “jumping or lying before a moving object,” a category that includes subway trains.

Subway suicides are public acts in which there is always one unwilling participant, the train operator.

“Very often the victims are looking you in the face when it happens,” a spokesman for the Transport Workers Union Local 100, Dave Katzman, said. Train operators must then step onto the track to make sure someone is indeed below the train. “That in itself can be a traumatic experience,” Mr. Katzman said.

Both the train operator and the conductor of yesterday morning’s A train were later administered drug tests, a standard procedure, and given time off. Counseling will be made available.

In addition to subway suicides there are fatal accidents. The Bureau of Vital Statistics found that 18 people died accidentally in New York City in 2003 after being struck by a railroad or subway train.

In all, 1,198 died in accidents that year.

The death at West 4th Street yesterday prompted talk among riders of placing barriers between platform and the track.

“I think they should have barriers because it’s so easy to push somebody,” one rider, Richard Turner, said. “We’re supposed to be the best city in the world. Things like this shouldn’t happen.”

The subway is one of the oldest transit systems in the country, with several types of subway cars, which would make barriers impractical, a spokesman for New York City Transit, Charles Seaton, said.

“The main issue here is that there are different types of subway cars, and the doors don’t line up,” Mr. Seaton said.

Not all who are swept under a subway car are killed. Last year, 34 people survived because they were caught between the rails or found refuge under the platform’s overhang. So far this year, 16 people have survived after being caught in the tracks under a subway car.

Yesterday at West 4th Street, wrapped in two white sheets, the dismembered body was lifted from the subterranean tracks and out of the subway.

Police removed their yellow tape. At 11:35 a.m. the A train left the station, revealing a tan-colored shoe and a pool of blood. Subway cleaners quickly got out their buckets. Express service resumed at 11:43 a.m. All that remained was the smell of bleach.