The Arlington County Board early Tuesday endorsed building a 4.5-mile streetcar line along Columbia Pike from the Skyline area of Fairfax County to the Pentagon City Metro station.

The 4-0 vote, with one abstention, came at 1:30 a.m., at the end of a seven-hour meeting devoted to Columbia Pike. It allows the county to seek federal funding that could cover 30 percent of the estimated $249 million cost of streetcar construction.

Board member Libby Garvey (D), who took office four months ago after winning a special election, partly on the basis of her skepticism about the streetcar, abstained from the vote. Garvey said she had not had enough time to study the issue thoroughly.

“I cannot see how a streetcar is anything more than a bus with tracks and overhead lines,” said Garvey, who is running for reelection in November. “Huge red flags are all over this for me right now. ... I am willing to be convinced by logic or data or fair comparisons, but I am not there yet.”

Her vote was not needed to pass the measure. The other members lined up behind the board’s 2006 endorsement of a streetcar line and compared its importance to the construction of Metrorail in the 1970s.

“I see light rail and streetcars as the next generation of a real rail system,” said board member Jay Fisette (D). “To me, this is an investment.”

The streetcar proposal, which has consistently provoked some local opposition, will be submitted to the Federal Transit Administration. If the project wins a federal endorsement and funding, Arlington plans to use state transportation funds to cover 14 percent of construction costs. The remaining 56 percent will be split 80-20 between Arlington and Fairfax counties. In all, the breakdown means Arlington will be on the hook for about $110 million, county staff said, to be paid by an existing commercial and industrial real estate tax.

The $199 million capital cost of the project, which was cited in the capital improvement budget that Arlington passed Saturday, includes federal and state subsidies, officials said Tuesday. The operating costs of the streetcar would come from the general county budget.

The board took up the issue of the streetcar at 11:45 p.m., after five hours devoted to Columbia Pike’s housing and land-use plan. It endorsed that plan on a unanimous 5-0 vote after hearing from nearly 50 residents.

The housing and land-use plan would offer developers more density for their projects if they preserve some of the 6,200 apartments and townhouses considered affordable to people who make less than the average median wage in the county. The plan could add thousands of new residents and transform the predominantly low-rise neighborhood of apartment houses and businesses into a more intensively developed enclave.

Board member J. Walter Tejada (D) voted for the housing plan and the streetcar plan with what he said was reluctance, after introducing measures intended to push for more money for affordable housing from developers and to preserve some of the most ethnically diverse neighborhoods in the county. Garvey objected to what she called the last-minute nature of some proposals, and Fisette said one proposal attempted to “back the board into a commitment” without proper study.

Board member Chris Zimmerman (D), who, like Tejada, lives in the Columbia Pike area, and who has been working on these development issues since 1998, took some of the credit for pushing the board into asking developers for more.

“Doing nothing serves nothing,” Zimmerman said, as a photo slide show of Columbia Pike residents played on the County Board’s large overhead screen. “I will be back.”