It is 4 p.m. on the corner of 8th and H streets NE. A cold misty rain falls from a dull winter sky and people going home stand taut and silent at the bus stop in front of a convenience store.

Inside the store, two men in hooded parkas watch as the anxious crowd presses toward an arriving bus. Their eyes, however, are riveted to the vehicle's rear doors. There, two men are attempting to sneak aboard.

As the men step onto the back of the bus, the hooded sentinels suddenly burst from the store and hurtle through the crowd. While other riders look on in disbelief, they remove the two errant passengers and lead them away. Moments later they have the two men in handcuffs and are reading them their rights.

Their parkas are open now. Pinned to their shirts inside are badges of the Metro Transit Police.

The scene is repeated every day at bus stops around the city. The two men in parkas are members of the transit system's undercover squad -- "Rollers" in street jargon. If The Rollers get you, a 60-cent bus trip home can quickly turn into a $50 ride to the nearest jail.

The two men arrested Wednesday afternoon at 8th and H NE were charged with fare evasion, a criminal misdemeanor under the D.C. code. As they stood with their hands manacled behind their backs -- seized for trying to avoid paying the 60-cent fare -- the two transit police officers searched their pockets. They removed money, papers and billfolds and examined each in turn. Moments later a D.C. police paddy wagon arrived and two burly policemen frisked the men up and down before putting them in the wagon and driving them away.

"I was trying to get an address," said one of the men.

"A dude was goin' to give me a transfer," said the other.

Soon they would be at 5th District police headquarters where they would be booked. The fine for fare evasion is $50 for the first offense. With each recurring offense, the fine doubles. Officials say a "significant number" of those arrested pay the fine on the spot; those who cannot pay receive a citation similar to a traffic ticket but are not jailed.

Metro officials said they have no idea how much money is lost each year to people who avoid paying bus and subway fares. "We have no firm numbers and no good guesses," said spokeswoman Marilyn Dicus. Each year, Metro spends more than $250,000 in police salaries alone trying to catch people evading fares or violating other laws related to the transit system. Since the undercover unit was formed three years ago, transit police have been arresting about 1,400 people each year for a variety of offenses. Most of the arrests were for fare evasion.

Officials are reluctant to provide precise details about the size of the undercover force or where and when it operates. More than 10 officers are involved. They ride the buses in civilian clothes, warning passengers against smoking, eating or drinking, and arresting those who ignore the warnings. They lurk around bus stops, nabbing those they find cheating on fares.

"We get a great bang for the buck," said Dennie Stuart, assistant chief of transit police, who estimated that four persons are arrested every day for trying to slip by turnstyles and fare collection boxes. "We get a great phantom effect when riders look around and see someone unusual. They say, 'Oh-oh. The Rollers are on the bus.' "

Cheating, officials say, is as old as mass transit itself. When the subway system opened wily passengers quickly developed methods of sidestepping fares. Metro recently purchased hand-held computer devices for station attendants to combat the "two-card shuffle," the use of one card for entering the subway and a second for exiting to avoid high fares into the suburbs.

But most prevalent, they said, is the illegal use of bus transfer tickets.

Passengers give the transfers away almost everywhere. Hands extend through bus windows offering them to people on the street. "They post them inside the bus shelters," said Stuart. "They stick them under the benches or between the glass and the metal frame."

Under the law, both the givers and the receivers can be fined, Stuart said, although usually only the ones on the receiving end are pursued. Police prefer to arrest people after they have tried to use the ill-gotten transfers and will climb into buses after them to put the handcuffs on them -- standard procedure in every fare arrest -- and pack them off to the nearest police station.

"We see them knocking on the bus windows yelling, 'Transfer. Transfer.' And people readily give them," said officer Terry Rychlik.

While officials shy from saying exactly where The Rollers are most active, and add that cheating crosses economic lines, they say fare evasion is most prevalent in the city's poorer neighborhoods. And though they contend many passengers are glad to see the fare system enforced, crowd reactions at bus stops are not always predictable.

One pair of officers, after making an arrest one Friday night, was assaulted by a mob throwing rocks and bottles. Stuart said such incidents are frequent, part of the job of being one of The Rollers.

"Nobody likes to see anybody go to jail," said Stuart. "For minor violations, they particularly don't like to see it."