Here comes Sarah Shain, typical Metro rider. The 22-year-old District resident is hustling down the left side of the escalator to the lower platform at Metro Center, clacking on the moving metal steps in her sensible pumps, until she hits a roadblock: a pair of tanned tourists in shorts standing two abreast, talking and blocking her path to the Orange Line train idling at the bottom of the escalator.

"The train is right there and you see the doors closing and it's like, 'Get out of my way!' " said Shain, a behavioral and social researcher who missed that train by seconds.

Then, a moment of empathy. "A lot of the people who visit here come here from Middle America where there is no subway, so they're not used to it," said Shain, who grew up in Kentucky. "You have to just expect that if you live in this city. You have to deal with the tourists."

This is the paradox of daily life in the capital of the free world, where every second counts. The people who live and work here take themselves seriously, striding purposefully with their written testimony, task force recommendations and briefing books. But it also is a place that attracts vacationers from around the globe, people who feel a familiarity with the city if only from all the television images and history books. They're drawn to the Metro, with its simple design, as welcoming and cheap transportation and even as a destination itself. Many locals have dueling impulses: They yearn to share Washington with the rest of the country, but they also just want to be on their way.

With record numbers of visitors coming to Washington -- 6 million are expected this summer -- and a growing daily Metro ridership that hovers at 690,000, encounters between visitors and locals play out on the subway each day. It's a cultural as well as physical clash -- tourists from Indiana wandering among impatient Washingtonians rushing to make their trains.

The conflict is most visible on Metro's 572 escalators. Because the subway was built deep beneath swampy Washington, Metro has more escalators than any other transit system in the world. A typical passenger must ride at least two escalators to reach a train. The steps are 40 inches wide, broad enough for just two adults.

Many stretch deep into the ground, including the 230-foot-long moving stairs at Wheaton, the longest escalator in the Western Hemisphere. To reduce accidents, Metro keeps the speed of its escalators relatively slow -- 90 feet a minute, compared with the 120 feet a minute that is typical of escalators at shopping malls, said Fred Goodine, Metro's assistant general manager for system safety and risk protection.

That means that riding the Wheaton escalator can take three minutes; and the Dupont Circle Metro's 2 minutes and 10 seconds. The escalator at Woodley Park Zoo/Adams Morgan, a favorite of tourists with small children, clocks in at 2 minutes and 20 seconds.

That may not seem very long, but to Craig Culp, it's an eternity. "I always walk on the escalators," said Culp, 44, of Gaithersburg, who daily sprints up and down the escalators at the Shady Grove, Metro Center and Eastern Market stations. "I'm not much of a rider. I'm just not comfortable standing still. I feel like I'm being incarcerated if I can't move on the escalator.

"There's a protocol," Culp said. "You walk on the left and stand on the right."

A pair of entrepreneurs launched StandtotheRight.com, a Web site that sells $15 T-shirts that make fun of the daily Metro collisions between tourists and locals.

One version is a black-and-white image of an escalator with the words Walk and Stand in the appropriate places. The other is an edgy revenge fantasy of someone rushing down a Metro escalator, pushing bodies out of the way. It says "Welcome to Washington, D.C., Now Please Stand to the Right."

"Why the hell is that moron from Ohio standing in front of you as you rush down the escalator and desperately try to make it to your train?" the Web site asks. "Because he hasn't been educated properly." The site advises riders to stand up for their "right to fly down the left side of the escalator, destroying everything in your path. No 'excuse me' is needed, let them read the back of your shirt as they try to collect their loved ones and luggage."

Although the influx of tourists, which grows thick in spring and summer, might irritate the daily commuter, Congress had visitors in mind when it began planning "America's subway" in the late '60s. The system was designed not just to ferry bureaucrats to their government offices, but also to serve as a national example of modern, efficient urban transportation.

The afternoon rush on Metro is generally more intense than the morning rush, with many commuters galloping through the busiest stations as if they are catching the last train that will ever run. Those running up and down escalators aren't easily categorized. One recent day at Metro Center, a young man scurried down an escalator, followed by several middle-aged men in ties, a disabled woman with a cane and an elderly man with a shock of white hair that bounced with his every step.

Tourists, meanwhile, seem content to stand and be carried by the machinery, oblivious to the stream of regular riders trying to move past them. Mothers load double strollers onto escalators, blocking everyone behind them. Groups of teenagers form circles on the moving steps. A couple of senior citizens from Tiffin, Ohio, stand side by side, holding hands.

"They don't know the rules of engagement," said Mozella Boyd Johnson, 44, a secretary for the District government, whose steady jaunt up the steep Dupont Circle escalator Thursday afternoon came to an abrupt end when she encountered a pair of men -- one carrying a heavy backpack and bedroll -- on a step near the top of the escalator. Johnson was dressed for walking, her feet in white sneakers beneath her pink floral dress, but she just resigned herself to ride the rest of the way.

Recent offenders include 21 fifth-graders from Westview Elementary School near Muncie, Ind., seven New York State Police troopers in gray dress uniforms and the Eichel family of Chapel Hill, N.C.

"I just didn't think about it," said Jim Eichel, a 57-year-old general contractor, who was standing to the left of his 84-year-old mother on the escalator from the Red Line platform down to the Orange and Blue Line platform at Metro Center at the height of the evening rush Thursday. Startled by an "Excuse me" coming from somewhere behind his shoulder and aided by a tug from his teenage daughter, Eichel tucked himself into a spot on the right side of the escalator.

"I didn't see a sign, did you?" B.J. Harris asked Jenyne Nelson as the two Realtors waited for an Orange Line train at Metro Center. The women, visitors from the U.S. Virgin Islands who were headed to see the new National World War II Memorial, had been scolded moments before by a regular Metro rider for blocking her path on an escalator. "She told us, 'If you're on the left side, please walk,' " Harris said. "I moved over and she said, 'Oh, tourists!' "

Years ago, Metro bolted small metal "Stand to Right" plaques to some escalators but then removed them, concerned that the message was an implicit endorsement of walking, something the transit system officially condemns. "We advocate that people do not walk, for safety reasons," said Goodine, adding that escalators are the place where most injuries occur inside Metro stations. Escalator injuries are declining but are still a major concern, he said.

"Unfortunately, we have this practice, and it's universal," Goodine said. "What are we going to do? Post a pedestrian traffic cop at every escalator? We have to come up with a way to address this, but right now our policy is, to ensure maximum safety, stand, don't run or walk, on the escalators."

Try telling that to Elizabeth Holbrook, 55, a paralegal from Arlington County. One recent afternoon, Holbrook barreled down an escalator at Metro Center, only to pause briefly at a cluster of five 20-somethings. She expertly insinuated herself into an empty space to her right, then to her left, weaving around them, like a running back.

"I've become quite an expert," she said. "I'm just very fleet of foot. Sometimes I say, 'Stand to the right.' Sometimes I just charge."

A family riding four abreast on an escalator at Metro Center risks the wrath of impatient commuters. Six million tourists are expected this summer.At Metro Center, escalator riders block the left side of the steps, inadvertently keeping walking traffic from passing.A ride on an escalator at Dupont Circle will take about 2 minutes and 10 seconds. The longest Metro escalator, at Wheaton, takes three minutes.