Three years after its splashy opening, the first phase of Metro's Silver Line has met with mixed success, fueling an unprecedented building boom in areas adjacent to its five new stations but struggling to attract riders.

Since 2014, 11 new high-rises have been built in Tysons Corner, and more than 2 million more square feet of development is in the pipeline. Big-name companies, including Intelsat, have relocated to Tysons, attracted by the promise of a walkable urban neighborhood with easy access to public transportation.

But of the five stations that opened in July 2014, only the end-of-line Wiehle-Reston station has come close to projected ridership. At three stops in Tysons — McLean, Greensboro and Spring Hill — ridership is a mere fraction of what planners projected in a 2004 environmental impact report.

In May of this year, for example, average daily weekday ridership was 1,618 at the McLean station, slightly below the 1,634 in May 2015 and well below the 3,803 the Silver Line was projected to serve in its first year of operation, according to the 2004 report.

To be fair, ridership of the Metro system as a whole is down. Between July and December of last year, overall ridership dropped 12 percent. Metro officials say chronic service disruptions and SafeTrack, an ambitious maintenance program that shut all or parts of the 40-plus-year-old system for the past year, have contributed to the decline.

Boosters of the rail line, however, say it is still too early to write off the Silver Line, asserting that as more developments are built near the stations, ridership will grow.

"I can't stress enough that ridership is a product of land use," said Shyam Kannan, managing director of planning at Metro. He said that the ridership projections came at a time when the economy was booming and were based on "heroic assumptions" about how quickly development would take place around the five new stations. These assumptions failed to materialize, he said, because of a combination of factors, including the 2008 recession, 2013 global economic collapse and, closer to home, sequestration and cuts to the defense budget. Those factors cooled the appetite for new construction.

"The good news is that things did unfreeze," said Kannan. "If you head out to Wiehle, you'll see nothing but construction cranes. All of that portends many thousands of trips on Metro."

Originally conceived in the 1960s, the $5.8 billion rail project is one of the largest infrastructure projects currently underway in the United States.

The 23.1-mile rail line is being built in two phases. Construction of the first phase, four stations in Tysons Corner and one in Reston, began in 2009 and was finished in 2014. Construction of the six stations in the project's second phase, including one at Dulles International Airport and two in Loudoun County, is underway. It is expected to open for passenger service in 2020.

Since 2014, when preliminary construction on Phase 2 began, regular users of the toll road have probably noticed new stations taking shape along that road and the Dulles Greenway.

On a recent day, crews at the Dulles Airport station were making preparations for the coming days when they'll install the escalators that will whisk passengers from the aboveground platform to the mezzanine below, where they'll head to the airport's iconic terminal to catch their flights. In the middle of the space, frames for four elevators cut through the ceiling to the passenger platform.

A bank of windows ensures that the area will be filled with natural light.

"This is going to be a nice area," Matt Ellis, senior superintendent for the Dulles station, said as he pointed to the windows and detailed some of the finishes that will be part of the final design.

Of the six stations, Innovation Center station in Herndon is the furthest along. Crews have already begun laying some track on the outbound portion of the station. In a vacant parcel on the station's southern side sit portions of the pedestrian bridges that, once assembled and set in place, will carry riders across the busy toll road to the station's entrance.

The Silver Line is being financed through a combination of local, state and federal dollars as well as special taxing districts. But the bulk of the project's expenses will be paid for by revenue from drivers who use the Dulles Toll Road — an element of the financing package that has angered those who argue that drivers shouldn't have to pay for the rail line.

Tammi Petrine of Reston is among those who have questioned the necessity of the project and whether users of the toll road should be the ones paying most of the cost. Three years out, she still has her doubts.

"I'm just not sure this huge expense of this heavy rail makes sense," said Petrine, a longtime community activist and co-chair of Reston 2020, a group dedicated to preserving the ideals on which Reston was founded.

Sharon Bulova (D), chairman of the Fairfax County Board of Supervisors, said that as more of the planned office, residential and retail developments come on line, she expects ridership to increase. Bulova and others view the Silver Line as critical to their effort to remake Tysons Corner into a walkable urban oasis where having a car is optional.

"I'm pleased with the extension of the Silver Line into Tysons and into Reston," Bulova said recently. "There has been a real recognition of the value of transit and rail."

The project could also fuel a building boom at Metro stations in nearby Loudoun County, long known as a bedroom community where having a car is a necessity. County officials say the arrival of the Silver Line will change that dynamic and attract those who prefer to ride rather than drive.

At the Ashburn station, for example, officials are contemplating plans by developers who want to build more than 2 million square feet of office space and more than 12,000 new residential units.

"This will change the character of Loudoun," said Phyllis J. Randall (D-At Large), chairwoman of the Loudoun County Board of Supervisors. She said that Loudoun will be unique among communities because it will be able to offer urban, suburban and rural living options to residents. The mix is also proving attractive to businesses.

"When I've talked to our development department, I've heard that a lot of businesses and corporations are looking to move to the area and are considering Loudoun because we will have the Silver Line."

Even with the building boom, Fairfax's Bulova concedes that ridership growth also will depend on the health of the system as a whole and whether transit agency officials are successful in their campaign to secure a significant source of dedicated funding to help pay for maintenance and modernization needs.

In many ways, concerns about the Silver Line's lackluster performance have largely been overshadowed by broader questions about the health of the overall Metro system.

Just six months after the new rail line opened, a Yellow Line train full of passengers stalled in a tunnel and filled with smoke. One passenger died, and more than 80 others were sickened.

In the months that followed, investigators and federal inspectors uncovered myriad safety violations and instances in which inspectors appeared to have falsified their reports. Eventually, federal officials intervened, taking responsibility for overseeing the safety of the transit agency's rail system — a temporary arrangement but one that continues today.

Metro's struggles to maintain its current system led some to question whether the Silver Line should have been built in the first place. One Metro board member even suggested scrapping the second phase. But others say that criticism is shortsighted.

"We're making a long-term investment in the region's future," said Stewart Schwartz, executive director of the pro-transit Coalition for Smarter Growth. "It has been absolutely worth the investment for Northern Virginia."

Metro officials are optimistic that some of the same problems — such as a shortage of rail cars, which strained Metro's existing system — will be resolved by the time the second phase opens in 2020. And because this portion of the rail line is brand new, it will already have the upgraded infrastructure — power systems, tracks — in place.

As for the dollars to maintain the current and expanded system, Bulova hopes that an agreement can be reached.

"Certainly, my intention is that when we cut the ribbon in [2020], that we have a funding plan in place to keep the system — the entire system — in a state of good repair," she said.