Metro’s Georgia Ave-Petworth stop. (Michael S. Williamson/The Washington Post)

THE MOST definitive and detailed recent study of Metro makes clear that the transit system’s problems are not mainly about management, spending or labor — though improvements are required in all those areas. Its overarching challenge is funding, according to a comprehensive study of the network by Ray LaHood, a former Republican congressman who served as transportation secretary in the Obama administration.

Mr. LaHood’s conclusion is not a surprise, though the evidentiary detail he summons is powerful. Metro’s surpassingly competent general manager, Paul J. Wiedefeld, and others who have scrutinized the 40-year-old rail system have also determined that reliability, safety and service levels will plummet without at least $500 million in new, earmarked annual capital funding.

“WMATA’s infrastructure is aging and needs renewal, and the funding it receives today is not enough to get this done. Not even close,” Mr. LaHood wrote in transmitting his report to Virginia Gov. Terry McAuliffe (D), who commissioned it. Metro’s “problems will never be solved without this new money.”

As a corollary to that conclusion, Mr. LaHood also recommended that Metro scrap its 16-member governing board — too big, fractious and parochial, in Mr. LaHood’s widely shared view — and replace it for three years or so with a five-member reform board. A credible board, Mr. LaHood told us, would soothe the “heartburn” that elected officials in Maryland and Virginia would otherwise have about pumping more dollars into Metro.

Let’s hope he’s right and that streamlined governance at Metro will coax Republicans in Virginia and Maryland to consider more funding. Unfortunately, until now many GOP lawmakers — particularly in Richmond, where many of them were just tossed out of office — preferred throwing up a smokescreen of ancillary issues to focusing on Metro’s dominant money issues. Mr. LaHood’s report makes clear that years of anemic capital spending contributed to a backlog of worn-out rail cars, tracks and other infrastructure whose cost of replacement and repair is now some $7 billion.

That’s an awfully big elephant in the room for Republicans to ignore — though many have managed nonetheless, preferring to harp on labor costs (average compared to those of other major transit systems, Mr. LaHood found), operating expenses (ditto) and mismanagement (mainly a thing of the past).

Mr. LaHood is not blind to Metro’s inefficiencies and failings. He thinks bus service is unsustainable and needs to be downsized; unionized workers should pay more into their retirement plans; and pensions should not reflect overtime earnings. Fare evasion by passengers is a problem, as is absenteeism among employees.

By and large, however, what distinguishes Metro from its peers elsewhere is not how much it spends but how much it receives, both from local stakeholders in Virginia, Maryland and the District and from the federal government, whose employees make up 40 percent of rush-hour passengers. Their failure to commit to ongoing, assured and adequate funding led Metro to its current woes. It’s on them to ante up to set the system up for a brighter future.