An artist’s rendering of the interior of planned Purple Line commuter trains in Maryland. (Purple Line Transit Partners)

A federal judge said Wednesday that it would make “common sense” for the Maryland Transit Administration to consider Metro’s “extraordinary” maintenance problems and declining ridership before it builds a light-rail Purple Line that would connect to it.

In hearing oral arguments in a lawsuit opposing the light-rail project, U.S. District Judge Richard J. Leon floated the idea — in apparent agreement with the plaintiffs — of requiring the state to analyze the potential impact Metro’s safety lapses and falling ridership could have on Purple Line ridership. The ridership forecasts were part of the cost-benefit analysis that the state did before deciding in 2013 to build a 16-mile light-rail line instead of a less-expensive bus option.

“We’ve experienced here in the District of Columbia, in this metro area, in the last month and a half, safety issues that appear to be of epic proportion in the entire system that appear to have shown a long-term impact on ridership,” Leon said. “I would think these recent major developments, with all the possible impacts they could have on [Purple Line] ridership, would be something that might really be valuable to know and think through . . . especially before $900 million in [federal] taxpayer dollars are committed, don’t you think?”

Metro’s recent decline is one of four major arguments that the Purple Line opponents — two Chevy Chase residents and a trail advocacy group — raised in their 2014 lawsuit against the Federal Transit Administration, the U.S. Fish and Wildlife Service, and the Transportation and Interior departments. The MTA joined the suit as a co-defendant in 2015.

Most of the lawsuit alleges that the state ignored or gave short shrift to the line’s potential environmental impacts, including storm-water runoff, endangered species, and noise for pedestrians and cyclists on an adjacent recreational trail. However, it was their argument regarding Metro that seemed to resonate most with the judge during the two-hour hearing.

The Purple Line, expected to break ground in November and open to passengers in 2022, will be owned by MTA and operated separately from Metro. However, Maryland officials have long touted the Purple Line as a vital east-west connection between the state’s three Metro lines and have estimated that 27 percent of Purple Line riders will use it to reach a Metro station. The line will run between Bethesda in Montgomery County and New Carrollton in Prince George’s County.

The judge’s apparent skepticism of government agencies’ arguments that Metro’s problems will have no effect on the Purple Line came two days before Maryland officials and a team of companies are set to financially close on a $5.6 billion contract to build, operate and maintain the line over 36 years. Pre-construction work, such as soil borings, began this spring, and state officials have said they expect major construction to begin this fall.

The judge called Metro’s safety and ridership issues “a dramatic change . . . of considerable proportion” that would seem to have a “likely correlation” with potential Purple Line ridership. He raised the idea of a “hypothetical” judicial order that would give the state up to six months to examine whether Metro’s safety problems and loss of passengers would have a “corrosive effect” on the state’s Purple Line ridership forecasts.

“It would be a critical piece of the analysis,” Leon said. “It’s kind of common sense, right?"

The judge said he will consider briefs that both sides may file in the next two weeks before making any decisions. He also floated the idea of requiring the state to make data used in its ridership forecast more available to opponents to allow their experts to independently review the projections.

Attorneys for the MTA and the Federal Transit Administration immediately objected to the idea of delaying the project by six months to do more ridership analysis. They stressed that a light-rail Purple Line will use different technology than Metro’s 40-year-old, heavy-rail subway system and will be operated and funded separately from it. The opponents are raising the issue, they said, as a way to try to stop a project they don’t like.

Linda Strozyk DeVuono, a lawyer for the MTA, said a six-month delay could jeopardize the state’s $5.6 billion public-private partnership on the project and allow the consortium of companies that won the contract to build and operate the line to back out of the deal. The state, she said, could then be forced to cover whatever costs the companies have incurred in designing the project.

Tyler L. Burgess, a lawyer for the Federal Transit Administration, said both federal and state transit officials have determined that any “short-term issues with Metro” would have no impact on Purple Line ridership. Three-fourths of the line’s ridership won’t depend on Metro, she said, and it’s “way too speculative” to suggest that Metro’s problems today will affect Purple Line ridership in 2040, the forecast year targeted in the environmental study.

Moreover, Burgess told the judge, Metro is making a “significant investment” in maintenance, referring to the nearly year-long SafeTrack program it recently began to speed repairs by closing sections of tracks and single-tracking trains around-the-clock in different areas.

“Any short-term problems the Washington Metro is experiencing, it’s demonstrating right now it’s committed to fixing,” Burgess said.

Burgess’s legal arguments didn’t include a key detail of the state’s 36-year contract, which requires the state to take the financial risk for how many people ride the line. To keep the line’s construction debt off the state books, the MTA has pledged to repay the private companies’ financing using only transit revenue rather than money out of the tax-supported transportation trust fund.

Because the Purple Line’s own fare revenues are expected to fall short of those payment obligations for the first 15 years, MTA officials have said they’ll make up the difference with fare revenue from the state’s MARC commuter rail system. That could leave less money for expanding MARC, which carries commuters between Washington and Baltimore, Frederick and West Virginia.

The plaintiffs — John M. Fitzgerald, Christine Real de Azua and Friends of the Capital Crescent Trail — argued that the U.S. Department of Transportation should not have approved the state’s Purple Line environmental review because federal law requires that a local transportation network have enough funding to operate and be maintained before federal money can be used to expand it.

MTA officials have said they expect to secure $900 million in recommended federal funding via a signed agreement with the FTA this summer. The FTA announced Wednesday that it had granted a $874.6 million low-interest “TIFIA” loan to Purple Line Transit Partners, the consortium of companies contracted to build, operate and maintain the line.

The rest of the line will be paid for with state money, contributions from Montgomery and Prince George’s counties, and private financing that the state will repay after the line opens.