Traffic gathers on Leesburg Pike near the Spring Hill (Tysons West) Station of the Silver Line Metro rail extension on April 29. (Jahi Chikwendiu/The Washington Post)

After years of construction work plagued by delays, Metro hopes to take a significant step next week toward eventually opening its new Silver Line, saying Monday that it plans to assume control of the project from the builder for up to 90 days of testing, possibly leading to the start of passenger service before summer’s end.

“For planning purposes, we’re targeting May 27” as the day the transit agency takes charge of the new rail line, Metro General Manager Richard Sarles said in a conference call with reporters. “That’s what we’re headed for right now, and it looks pretty attainable.”

The announcement is a big move forward for the project, which has been hampered by numerous setbacks, including problems with the automatic train-control system (a key safety feature), the mistaken installation of hundreds of station speakers that did not meet fire code requirements and the abrupt resignation of the project’s top manager last month.

Officials from the Federal Transit Administration and the Tri-State Oversight Committee, which oversees Metro’s operations, still must conduct their own independent safety reviews. Sarles said that will happen during the 90-day testing period. Both agencies must sign off on the rail line before it can open to passengers.

The start of testing May 27 would raise hopes that trains carrying commuters could begin running in late July or early August. Although Metro has 90 days to complete its testing, Sarles has hinted that the transit authority might not need the full three months.

Monday’s announcement also is welcome news for officials at the Metropolitan Washington Airports Authority (MWAA) and the authority’s beleaguered contractor, Dulles Transit Partners. Both have been criticized for they way they have managed the construction .

Running from the new Wiehle-Reston East station in Fairfax County, the Silver Line will connect with Metro’s Orange Line in East Falls Church, then follow the tracks of the existing Orange and Blue lines across the Potomac River from Rosslyn and through the core of downtown Washington. A later phase of the project will extend the Silver Line from Wiehle-Reston East to Dulles International Airport.

Dulles Transit Partners, led by construction giant Bechtel, was seven months late in completing work on the first phase of the $5.6 billion project.

At one point, it appeared that Bechtel might have to pay huge fines, perhaps in the millions of dollars, for not meeting its deadline. The Silver Line is one of the largest infrastructure projects of its kind being built in the United States.

To hasten the eventual start of passenger service, Metro recently decided not to wait until construction was finished before starting its 90-day test period. As a result, while Metro train operators and other employees familiarize themselves with the line and simulate the conveying of passengers, the contractor will continue working.

Discussing the start of passenger services, Sarles said Monday: “Again, to reiterate, probably the most important thing is that the contractor for MWAA, Bechtel, gets the work done that they said they would do.”

He added that there are “about 30 items or so that have to be completed,” none of them seemingly major. They include work on station public-address and fire-alarm systems, the replacement of some faulty track-circuit components, and the addition or repair of some features on station escalators and an elevator.

“Once they’re completed, we’re ready to go,” Sarles said, although, as in the past, he declined to be specific about when he thinks passenger service will begin.

“Sometime in June, after I have a better sense of where the Tri-State Oversight Committee is, and the progress being made by the contractor, then I will be in a better position to speculate about when the date is.”

Before it intersects with the Orange Line, the Silver Line’s first phase is 11.7 miles long with five stations, four in Tysons Corner and one in Reston at Wiehle Avenue. Its estimated cost is $2.9 billion. The project is roughly $150 million over budget. And with still more work to be done before it is open to passengers, some believe its price tag will rise.

Nearly half of the rail line’s two-phase, $5.6 billion cost is being paid by users of the Dulles Toll Road. Fairfax and Loudoun counties, MWAA and the state of Virginia also are providing funding. The federal government contributed $900 million to the first phase.

Originally, Metro had hoped to begin passenger service on this first leg in December 2013, but a series of delays forced officials to push back the opening.

The delays have been costly for Metro, which is losing $2 million to $3 million in potential revenue in each month that there are no passengers on the Silver Line.

Speculation on when the rail line will begin carrying passengers has become a parlor game for those who have monitored the Silver Line’s progress. With the stations mostly complete and some test trains being run, passersby have been fooled into thinking that the Silver Line is open for business.

The Silver Line is the first full line to be added to the 38-year-old Metro system in more than two decades. It also is the first line not built by Metro. Instead, MWAA was put in charge of overseeing and managing construction of the line, which will be run by Metro.

During the 90-day review period, Metro also will conduct emergency drills with first-responders from around the region to familiarize them with the new rail line.

Preliminary work on the second phase of the Silver Line, which will extend service to Dulles and into Loudoun County, is underway. Officials expect to begin construction sometime this year. Phase 2 will be built by a different contractor, Capital Rail Constructors, led by Bethesda-based Clark Construction.