The Pennsylvania Department of Transportation classifies all 25,000 of its structures 8 feet long or longer as bridges, whether they're long river crossings, short overpasses, curving ramps or small culverts.

And 25 percent are rated deficient by federal engineering standards because of deterioration, old age, weight restrictions, outdated construction or inadequate capacity -- or a combination of problems.

Only Oklahoma (31 percent) and Rhode Island (26 percent) are worse off, but both states combined don't own as many bridges as PennDOT.

It's part of a bridge crisis that has haunted the state for three decades and is 20 years and at least $10 billion away from attaining a manageable situation.

"Of all the needs we face, none is greater than our bridges," Gary Hoffman, PennDOT deputy secretary for highway administration, said yesterday after he inspected the collapsed overpass on Interstate 70 in Washington County. "You can have a road failure; that's not catastrophic. A bridge failure is."

This year, PennDOT met its higher goal of bidding out $400 million worth of bridge construction and rehabilitation and $50 million in bridge preservation work, a total of $450 million.

"The department has been increasing bridge expenditures since the late 1990s [after the last big gas tax increase]," Mr. Hoffman said. "This administration stepped up to the plate in a big way. Next year's goal is to ramp up to $500 million. We need to spend at least that much every year for the next 20 years."

An analysis of data by the Road Information Program disclosed another alarming statistic: The Pittsburgh region has a higher percentage of structurally deficient bridges than any other part of the state.

Research Director Frank Moretti of TRIP, a Washington, D.C.-based organization funded by the highway construction industry, speaking at a conference in Harrisburg last month, said the state's aging bridge infrastructure is starting to seriously affect the state's economy and mobility, notably in the rural areas where many closed and posted bridges are located.

The American Society of Civil Engineers says Pennsylvania's bridge crisis is more serious than TRIP claims. It called 42 percent of the state's bridges "structurally deficient or structurally obsolete."

In either case, the news is not good.

"But it's a problem that folks understand more than anything else," Mr. Hoffman said.

Before 1997, when the General Assembly last raised the gasoline tax, along with registrations, licenses and other fees, PennDOT was spending about $150 million a year on bridge repairs, or about one-third of this year's expenditures.

Even at the rate of spending $500 million a year for another 20 years, an estimated 10 percent of PennDOT-owned bridges would still be structurally deficient.

Figures don't include bridges owned by municipal entities, from counties and townships to the Port Authority of Allegheny County, which owns 66 transit bridges and 11 highway bridges inherited when it was formed in the early 1960s.