Structurally deficient bridges are not imminently dangerous, the group emphasized, but they need repairs. More than 63,000 bridges fall into that category nationwide.
Pennsylvania's raw numbers and percentages of structurally deficient bridges are the highest in the country, the association said.
Nine of the commonwealth's 10 most traveled bridges considered unsound are in the Philadelphia region, each carrying tens of thousands of vehicles per day. Six are on I-95 in Philadelphia, two are on the Schuylkill Expressway in Montgomery County, and one is on the turnpike, according to the association.
New Jersey fared better than Pennsylvania, with 10 percent of its 6,566 bridges deemed deficient, rating 29th nationally. The Walt Whitman is cited for the portion that runs over I-676 southbound and the Delaware River in Camden County.
The report echoes pronouncements that have been made by various groups for years about Pennsylvania's bridges. Erin Waters-Trasatt, a state Department of Transportation spokeswoman, says the agency is "well aware of this concern."
Unlike in years past, however, Waters-Trasatt noted that PennDot is set to repair about 700 bridges this year, thanks to the $2.3 billion transportation funding bill passed by the legislature in November.
In addition, she said, the number of state-owned bridges considered structurally deficient has decreased, from about 6,000 in 2008, to around 4,200 as of March. That analysis was based on the Federal Highway Administration's National Bridge Inventory from 2013.
"It is something that is definitely on PennDot's radar," she said, noting that the exact numbers reported by PennDot and the association vary slightly because of how each agency classifies bridges.
The association used Thursday's report to advocate for more federal funding to be directed toward road and bridge repair.
Alison Premo Black, the group's chief economist, concentrated in particular on the Highway Trust Fund, which provides money for road and bridge construction across the country.
Failing to reinvest in the fund, Premo Black said, would place an undue burden on states and municipalities to finance such projects.
"Significant levels of sustained investments" are needed across the country, she argued.
A spokesman for U.S. Sen. Pat Toomey (R., Pa.) said Toomey "believes that funding road and bridge repair is an essential function of government," without addressing the Highway Trust Fund specifically.
A spokesman for U.S. Sen. Robert P. Casey (D., Pa.) agreed. "This report drives home the need for federal investment in Pennsylvania's aging bridges. . . . In the coming months Congress should take up the opportunity to pass a long-term transportation bill that fixes these bridges."
While Premo Black cast a gloomy outlook on the state of bridges nationwide, she did commend the Assembly's transportation bill, which earmarked about $1.6 billion for bridge and road repairs.
"I think that's a very positive example of your elected officials taking steps and taking action," she said.
In Montgomery County, Commissioner Leslie S. Richards said the commissioners have pledged to invest about $38 million in county funds to upgrade locally owned bridges, in addition to the boost they hope county bridges will receive from the state transportation bill.
While repairing bridges may not be a headline-grabbing task, Richards said, failure to do so could cause headaches across the region. "If we don't take care of them, they're going to start to close one by one," she said. "And it'll make our roadways an absolute mess."