A view of H Street Northeast in Washington. Mayor Muriel Bowser voiced her support, during speeches recently, for the District's street car line and plans for expansion of the system. (Nikki Kahn/The Washington Post)

After years of swelling budgets that funded a smorgasbord of potential lines, the District’s struggling streetcar system is being put on a diet.

Mayor Muriel E. Bowser (D) on Thursday jettisoned any near-term plans for building a broad streetcar network, releasing a budget that focused narrowly on a single east-west line.

Bowser proposes spending about $54 million over three years on streetcars. That represents a more than $160 million drop-off from the previous spending plan covering the same period.

The move represents a strategic shift by the new Bowser administration toward a much more conservative approach for a project that has been marked by delays, management shortcomings and safety concerns.

“The streetcar program that we inherited was actually a 37-mile proposal,” Bowser said shortly after unveiling her first citywide budget. “This budget doesn’t speak to 37 miles.” The new estimate: 7.5 miles.

Bowser’s top transportation official, Leif Dormsjo, said the administration has rejected the previous approach of having multiple would-be streetcar segments ­“flying in loose formation.” In its place will be a determined and methodical approach designed to open, expand and make successful a single line, Dormsjo said. Work on a long-planned north-south streetcar line from Takoma to Buzzard Point, for instance, will wind down after some current efforts are completed, he said.

Longtime streetcar backers were pleased the system survived an administration review to determine whether it should open or expand at all. But they also said they were concerned about the prospect of retrenching too far.

“We shouldn’t stop thinking about how the streetcar can be one of our transit choices across the city, both north-south as well as east-west,” said D.C. Council member Charles Allen (D-Ward 6), an early backer of the still-unopened ­2.2-mile line on H Street and Benning Road NE. “I’d like to see us have some planning dollars to continue working toward the future. But we obviously need to have the H Street line be successful. That’s where I’m going to put my energy.”

Bowser, during her State of the District address Tuesday, promised to extend that line east to the Benning Road Metro station and said she wanted residents to be able to take streetcars “eventually all the way to Georgetown.”

The $370 million the District Department of Transportation proposes to spend on the east-west line in the six-year budget period falls short of what it would cost to expand to the Benning Road Metro and complete the line to Georgetown, according to DDOT.

In addition to the $335 million Bowser sets aside for the streetcar project in her budget — most of which is earmarked for the latter half of the six-year period — there would be more than $30 million in ­“carryover” balances from previous years, according to DDOT.

The spending breakdown would be $41 million for the existing H Street/Benning Road line, including construction of a maintenance facility; $130 million for the extension to the Benning Road Metro; and $198 million for the line from Union Station to Georgetown, according to DDOT. Funding needs for a line to Georgetown “will extend beyond” the proposed capital improvement plan, DDOT said.

One route to Georgetown favored by city transportation officials in recent years would cost about $340 million, according to a federally funded study. Some federal funds could also supplement District spending on that project, officials said.

Estimates for the cost of extending the line to the Benning Road Metro station have varied. According to a 2013 DDOT report, that extension would cost more than $80 million, not including major expenses such as right-of-way acquisition, bridge reconstruction and repair costs for a key intersection. DDOT now estimates it will spend about $130 million on the project over six years.

Council member Mary M. Cheh (D-Ward 3), who chairs the panel’s transportation committee, said Bowser’s decision not to include more streetcar construction money in the next fiscal year is a reflection of the mayor’s overall priorities.

“I’m making an assumption she’s taking all of that capital money to pay for her initiatives for affordable housing and other things,” Cheh said. But Cheh also said the spending slowdown also represents “a breather to let DDOT reboot the whole system, because they inherited a terrific mess. I guess they have to start right at the bottom and build it back up.”

Cheh said she is considering pushing to put in “some benchmarks” for DDOT to meet before it is provided “even with the reduced millions.” “In other words,” she said, “you can have the money” but with conditions. “Given the past mess, I think that a certain bit of modesty here is probably called for. . . . But I don’t want to think of this as the endpoint. I want to think of it as proving we can do this and adding other pieces as we go.”

Bowser’s budget describes long-term hopes for a bigger streetcar network. Her six-year funding plan calls for spending $533 million, including funds for replacing the Hopscotch Bridge behind Union Station, which is about $54 million less than in the current six-year plan. The 37-mile plan was projected to cost about $3 billion.

“It is anticipated that by 2030 a comprehensive streetcar network will operate in conjunction with the Circulator, Metro Extra rapid bus, and bus rapid transit to complement the current Metro bus and rail system,” according to the current proposal.

For Metro, Bowser’s budget proposes fully funding the Washington Metropolitan Area Transit Authority’s operating revenue request and providing $791 million for capital improvements over six years.

Metro spokesman Dan Stessel said the money would allow Metro to avoid fare hikes or the kind of “significant service cuts” that had been under consideration to close a budget gap, such as running trains less frequently during rush hours.

That’s “good news for Metro riders. . . . Certainly the mayor’s support in her budget, as well as support from Virginia and Maryland, made that possible,” Stessel said. The capital funds also could be used to take advantage of options to buy 220 additional new rail cars at favorable prices, Stessel said.