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Solutions, which are just being formulated by Metro, are as ambitious as the original plan to build the subway. Among the ideas being studied are new downtown rail lines that would separate the Orange from the Blue line and the Yellow from the Green, new exits at busy stations and extensions to mezzanines that would protrude over the train tracks.

"We have to take the system apart and then put it back together again," said P. Takis Salpeas, a Metro assistant general manager.

Alternatives

Some question whether the region should pour its resources into transit, when the roads and bridges are the second most congested in the country, behind those in Los Angeles.

"I don't think anyone questions that mass transit is a fundamental part of our transportation system today and in the future," said Bob Chase, of the Northern Virginia Transportation Alliance. "At the same time, the reality is that mass transit carries 5 or 6 percent of the total daily trips made in this region. . . . You have to evaluate this in terms of the amount of money being spent and the number of people being moved."

Given the fact that resources are limited, such alternatives as highway investment must be analyzed, Chase said.

Others say Metro's problems boil down to a chronic lack of rail cars, nothing more. "The weak link in the system since 1976 has been shortages of rail cars," said Zachary Schrag, a Columbia University graduate student writing a history of Metro. "The actual opening was late because they couldn't get the rail cars ready in 1976. It happened again in the '80s with the [Yellow Line] extension to Huntington and again with the Green Line opening to Branch Avenue. They've got all this beautiful track and nothing to run on it."

The Metro system was designed to run eight-car trains, but Metro has never owned enough rail cars or faced the demand to run trains that long. Today, it operates four- and six-car trains.

"If they went to eight-car trains, they'd instantly increase capacity by 30 percent," Schrag said. "The region could grow quite a bit without necessarily having congestion in the core."

Longer trains alone can't solve Metro's problems, White said. The subway designed in the late 1960s is simply not sophisticated enough to handle the demands Metro is facing, Salpeas said.

Design Limits

Many of Metro's capacity problems can be traced to its design. It was built as a two-track railroad, with five lines stretching from the city core to the suburbs in a hub-and-spoke arrangement.

The two-track design means big trouble when a train breaks down. The train has to be hauled down the track until it reaches one of just a few sidings where it can be pulled off the main track. That slows movement on the entire line and explains why a breakdown at Farragut North can affect passengers waiting for trains at Union Station.

"We're like a two-lane country road with no breakdown lane," White said.

The two-track railroad also prevents Metro from running express trains. And 24-hour service is out of the question, because Metro needs to shut down its system several hours a day to perform track maintenance. Larger systems such as New York's, which has up to six tracks at some stations, can perform maintenance on two tracks while running service on others, and can operate round-the-clock.

The other crucial flaw is the fact that four of Metro's lines share track for significant stretches. The Orange and Blue lines, for instance, merge at Rosslyn, then share track through a tunnel under the Potomac River and across downtown Washington until they separate at the Stadium-Armory Station.

Forcing the lines to share track cuts the capacity of each by half and is the main reason inbound Orange Line trains at, say, West Falls Church are standing room only during rush hour.

Because a certain distance must be maintained between trains, there's a limit to the number of trains that can be sent down the Orange and Blue track each hour. Plans to extend rail service to Dulles and Tysons Corner may help ease crowding on the roads in an area that lacks rail service. But lengthening the Orange Line to Dulles will exacerbate crowding, by reducing the capacity of the Orange and Blue lines even further.

Remodeling Lines

There is new signal technology that may allow Metro to run trains closer together and thereby squeeze an additional train or two onto the Orange and Blue lines. But the better solution is to separate the lines. That would mean building a new track through downtown, an expensive solution that would require tunneling through the middle of the city as well as a new tunnel under the Potomac.

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