She has been part of our lives for nearly a decade -- her soft melodic voice that says "Doors closing" on the Metro trains. One day soon, those doors will slide shut on her final ride.

Coming in her place will be the voice of a man telling people to get ready to exit -- and fast.

Losing Sandy Carroll's mellow voice is the first step of several Metro decided yesterday that it will try to smooth the flow of humanity through the country's second-busiest subway system, behind New York's. In a transit system bulging with a record 707,885 riders a day, the movement of people in downtown stations is not orderly. It is not calm. It is not pretty.

Crowds are gumming up the works. Clashing armies of commuters block each other from reaching trains or escalators. Passengers waiting to board rail cars smash into those trying to leave. Most horrifying to Metro officials, these chaotic dances delay the trains.

After pondering the problems for five years, the Metro board of directors approved several pilot projects that will start in February, aiming to move people on and off trains and escalators with speed, grace and, maybe, civility.

"We're trying to move as many trains through the system as we can," said Jim Hughes, Metro's acting assistant general manager for operations. "Part of that is cutting the amount of time in the stations and getting people on and off as quickly as we can."

Many train delays are caused by riders dashing into cars at the last second. "The message and the door chime have become a little like the yellow signal on a traffic light," Hughes said. "The purpose of the chime is to tell people to step back, that doors are closing. But our customers hear that, and they run to get on a train. . . . It's got to be a different voice, something that sounds different, because right now it's background noise."

The engineers who designed Metro counted on trains spending about 15 seconds in each station to let riders get on and off before moving on. That worked when Metro opened in 1976, and ridership was low.

But now, trains are spending 30 seconds to 35 seconds in the busiest downtown stations, Hughes said. Any longer, and Metro's ability to run the maximum number of trains during the peak hour will start to be hampered, he said. Several months ago, Hughes dispatched an internal team of architects, engineers, station managers, train supervisors and escalator experts to videotape the way people move around stations and find low-cost improvements.

To help smooth the emptying and loading of trains, Metro will test platform markers at Union Station, Gallery Place-Chinatown and Metro Center. The markers will indicate where to line up with rail-car doors once a train pulls into a station. The idea is to get people ready to board before the train arrives and out of the way of exiting passengers. Although most riders wait at the sides of the doors to give passengers room to exit, plenty of people plant themselves directly in front of the doors. A brazen few try to muscle their way on while people are getting off.

Nearly every other major U.S. subway -- including systems in Chicago, Boston, San Francisco, Philadelphia and New York -- uses platform markers. Metro officials studied them and debated possible styles: Arrows with circles? Arrows spaced far apart? Colored panels instead of arrows?

They settled on six options to present to the board yesterday. Board members narrowed the choices to two. One option has arrows with circles; the other has arrows without circles. They opted for the widely spaced arrows.

Temporary markers will be put in the test stations in February. If they're successful, Metro will install permanent tile markers systemwide.

Platform markers assume a train is going to stop at the same spot every time, something Metro has had trouble delivering. Robert J. Smith, who represents Maryland on the Metro board, observed that Metro trains routinely overrun platforms. Operations reports show this happens every day, sometimes as many as five times a day.

"It is Washington, and we've got a lot of legal minds, and someone is going to stand on that arrow and hold his ground, and that train is going to stop over there," Smith said, motioning several feet away. "And he's going to be angry because here he is, standing where we told him to stand, and you know he's going to be one of the 7,000 calls we get the next day."

Metro officials also studied whether passenger collisions on escalators could be reduced by changing their directions. At the L'Enfant Plaza station, for example, two side-by-side down escalators dumped such a flood of passengers onto the Vienna/Franconia-Springfield platform that riders couldn't get off some trains, Hughes said. Three weeks ago, a switch in the pattern from down-down-up to down-up-down eased the mess, he said.

On its 588 escalators, Metro intends to paste large stickers that say "Stand to the Right," a cue to out-of-towners that Washingtonians are not content to just stand and ride but often walk -- or run -- on the left side. Metro has more escalators than any transit system in North America, and the conflict between those trying to walk on the left and those standing in their way has become a daily aggravation.

"We're finally going to do this?" asked Chris Zimmerman, who represents Arlington County on the Metro board. "Hurray!"

But the idea is not new in Washington. Until about seven years ago, Metro escalators had metal plaques that read "Stand to Right." But an internal task force decided that those signs implicitly encouraged people to stand on the right and walk on the left, which Metro managers said was unsafe. So they ripped the signs off -- which cost time and labor but did not stop anyone from walking on the left.

"If you can't beat 'em, join 'em," said Metro spokeswoman Candace Smith.

Metro wants you to follow the arrows at train stops. For other changes, see A12.