Packed tighter than a sushi roll Subway: Through wars, disasters and terrorist attacks, Tokyo subway trains keep rolling, with passengers nearly cheek to cheek during rush hours. A warning to female riders: Watch out for wandering hands.

TOKYO -- At 7: 50 a.m., the subway train pulls up to the platform, but the train is already jam-packed. Men and women are sitting in the cars, standing in the cars, crammed against each other, shoulders bumping, hips rubbing, eyes averted politely, stoically. There's not an inch to spare.

Or maybe there is. As chimes sound to warn the passengers that the automatic doors are about to close, Reiko Yamaguchi skids to a stop on the sparkling white platform. She bows deeply to those already on the car. Then she flings herself into it. The mass of passengers heaves like a gigantic caterpillar.

She's in.

And, whoosh! the train is gone.

This is morning rush hour. For Yamaguchi and nearly 10 million other Japanese, the daily trip from home to work is a hurly-burly, headlong rush that stands out against the backdrop of a society renowned for courtesy and decorum.

There's good reason to hurry. Tokyo's 12 subway lines carry about 3 billion passengers a year -- nearly three times the number carried by the New York subway (and about 270 times the 11.6 million passengers carried by the subway in Baltimore).

The Tokyo metropolitan area is home to nearly nearly 27 million people, the world's largest megalopolis. Of those 27 million, about 8 million live within Tokyo proper. But each day, 9.5 million suburbanites arrive via 2,401 subway cars.

And the crunch is greatly exacerbated by the fact that 30 percent of all the passengers -- about 3.5 million people -- ride the subway in the same hour, between 8 a.m. and 9 a.m. So every day, for that hour, an onslaught of commuters change the pristine white corridors of the subway stations into packed, steamy tunnels resembling an ant farm gone berserk.

The passengers stand in neat queues, waiting politely for a train to arrive. But the sight of an open train door has an extraordinary, immediate effect.

There are tales of women fainting on the subway (overcome by the crush). There are complaints about the confusion (one station has 41 separate exits to the street). There are opportunists, called chikan, who use the crowds as a cover to grope and fondle female passengers; this is so much a fact of life that one chikan has published a "how-to" book. All of which may account for why, when describing her 80-minute trip to work, Yamaguchi uses the phrase "American football."

The secretary demonstrates her subway strategy: Duck head, tuck shoulders inward and cross arms in front of chest. In this offensive-defensive position, Yamaguchi can slither into tiny gaps in the crowds. Once there, her hunched back and shoulders shield her torso from large purses, umbrellas, sharp elbows and occasional wandering hands.

From 5 a.m. until just after midnight, trains pull up to the 155 stations. During peak hours, only two minutes may separate arrivals. Since the opening of the first line, in 1927, the system has never completely shut down.

During World War II, when most of the city's male population was in the military, women ran the trains. Some trains have been halted by earthquakes. (Indeed, there are seismometers along the subway lines.) And about 30 times a year, trains have to be stopped because someone has thrown himself onto the tracks.

The number of suicides is decreasing, says Kiyohide Maemura, chief of information for the Teito Rapid Transit Authority, a drop he attributes in part to changes in the subway system: brighter lights in the tunnels, more brightly colored walls in the stations and a system of doors (in one station so far) that prevent anyone from getting near the tracks until a train arrives at the platform.

Suicide "is a very serious problem," says Maemura, "because it brings us trouble for the customers, it stops the line."

Perhaps the ultimate proof of the subway system's importance was the nerve gas attack in March 1995 by the religious cult Aum Shinri Kyo. The gas killed 11 people and injured more than 3,000 -- but authorities shut only three of 12 lines, and ridership figures returned to normal within a few days.

"At first, there was a psychological effect, and some people refused to take the subways," Maemura says. "But the practicality won out."

To reduce potential hiding places for a bomb, authorities removed all the trash cans from the subway stations. Rather than litter, commuters both carried trash to their offices and virtually stopped buying anything that would produce waste. Sales at newspaper stands dropped, and vending machines offering drinks were taken away. "There were a lot of complaints at first," says Maemura, "but human life is more important than a little inconvenience."

"When it comes to that kind of stuff -- like littering -- the Japanese are very good about it."