The Francis Scott Key Bridge in Washington, D.C. (J. David Ake/Associated Press)

Under the glare of floodlights, as late-night drivers and early-morning commuters shared the same traffic backup before dawn Thursday, three lanes of the Capital Beltway closed to let repair crews patch a mega-pothole on the bridge over Kensington Avenue.

It was a bad pothole on an otherwise sound bridge, but the potential for bridge repairs to gum up the works was telling on a day when new federal data revealed that there are 63,000 U.S. bridges in need of more significant repair.

“These are bridges where drivers and first responders are crossing over 250 million times each and every day,” said Alison Premo Black, an economist with the American Road and Transportation Builders Association, the group that compiled the federal data.

Although there have been some dramatic bridge collapses in recent years, the 63,000 bridges judged structurally deficient are not all about to fall down. Bridges deemed on the verge of collapse are closed.

In a sense, the problem is more insidious than that. When budgets are tight, states and counties often have to put off repairs to bridges and roads. The traditional source they rely on for federal dollars — the Highway Trust Fund — is projected to run into the red this summer.

That has left state and local highway officials in limbo, waiting to see if Congress finds a new revenue source to supply the dollars they need. In some states, half of transportation funding comes from Washington, and until local officials know whether they can expect that to continue, they are loath to launch multi-year projects to renew or replace bridges and roadways.

“Over the last 15 years, state DOTs and local governments have been making significant investments to improve some of these bridges, but they simply don’t have enough funding to address the problem,” Black said.

With an ample boost in federal money, $100.2 billion was spent by governments on all levels in 2010 on capital improvements for the nation’s 604,493 bridges and 4.1 million miles of roads.

That sort of spending brought progress in the first decade of the 21st century, leading to a slight decline in the number of deficient bridges.

But with much of the nation’s post-World War II infrastructure wearing out and the federal gas tax that built it steadily declining, experts say more than $1 trillion of investment is need to shore it up.

“We would suggest that signs be posted on structurally deficient bridges so people know what they’re traveling over,” Black said. “Sometimes bridges on this list do fail. The I-35 bridge in Minneapolis that collapsed in 2007 — that bridge was on the structurally deficient list.”

Deficient bridges — those rated poor or worse because load-carrying elements have deteriorated — can affect consumers. As bridges continue to decline, weight restrictions often result. When trucks delivering shipments to market take longer, roundabout routes, prices can increase.

Almost 64,000 bridges nationwide have posted load limits or restrictions reducing the load they previously carried.

Pennsylvania, with 5,218 deficient bridges — almost one-quarter of its spans — has the nation’s worst problem. In contrast, the three jurisdictions in the Washington region are in good shape. The District has 21 troubled bridges, 8 percent of its total number. Maryland has 333 deficient state and county bridges, 6 percent of its total. Virginia has 1,186, 9 percent of its total.

All three jurisdictions get about half of their annual highway funding from the federal government, with Virginia leading the way at 57 percent.

The three provided the Federal Highway Administration with projections of how much it would cost to address all their deficient bridges. Virginia estimated the cost at $7.3 billion, Maryland said $1.6 billion and the District put the figure at almost $467 million.

Richmond and Virginia Beach are home to most of Virginia’s 10 most heavily traveled deficient bridges, but one is on Interstate 66 in Arlington County. The state’s four busiest deficient bridges are on I-95 in Richmond at Lombardy Street, Overbrook Road, Robinhood Road and Sherwood Avenue. Two bad bridges in Virginia Beach are on the Lynnhaven Parkway and London Bridge Road.

The District’s busiest deficient bridges were the Key Bridge, the Memorial Bridge and the Park Road connection on the Anacostia Freeway. Others on the federal list included the South Capitol Street crossing of the Anacostia, two on Anacostia Freeway, the East Capitol Street bridge over the Anacostia, a ramp to route 50 and the bridge that carries 16th street NW over Military Road. One bridge that made the 2013 federal list, the New York Avenue bridge over Washington Terminal, has just been rebuilt.

Half of Maryland’s 10 busiest bad bridges were in Prince George’s County, four of them bridges where I-95 meets the Suitland Parkway or Suitland Road, and the fifth is on I-95 a mile and half north of route 210. One of the state’s most heavily traveled deficient bridges is on the Baltimore beltway at Milford Road. Two others also are on the Baltimore beltway at Leeds Avenue and a mile north of route 1. Another was where I-95 meets Route 32 in Howard County.