A report released this week by the American Road and Transportation Builders Association (ARTBA) shows that 1 in 10 bridges in the United States is structurally deficient and in need of repair. Structurally deficient bridges are crossed more than 250 million times every day by cars, trucks, and buses.

Bridge decks and support structures are regularly inspected by state transportation departments and are rated on a scale of one to nine, with nine meaning that they are in “excellent” condition. A bridge is classified as structurally deficient and in need of repair if it receives a rating of four or lower. The ARTBA report explains that the number of bridges fitting this description reached 63,207 in 2013, and that altogether these structures measure 1,500 miles in length. That is the equivalent of driving from Miami to Boston, a trip that would take more than 25 hours to complete.

The states with the greatest numbers of structurally deficient bridges are Pennsylvania (5,218), Iowa (5,043), Missouri (3,357), and California (2,769). In four states—Pennsylvania, Rhode Island, Iowa, and South Dakota—at least 20 percent of all bridges fall into the deficient category. In 14 other states at least 12 percent of all bridges have been similarly categorized.

Dr. Alison Premo Black, ARTBA’s chief economist, explained that “some of the most heavily traveled bridges were built in the 1930s. Most are more than 40 years old.” Most of these older, heavily-traveled bridges are part of the interstate highway system, the result of the largest public works project ever undertaken by the United States government. Since 1956, this system has reached 46,876 miles in length and carries 24 percent of all highway travel.

This report underscores the impact of the collapse of federal support for the interstate highway infrastructure in recent years. Many states are experiencing a slowdown in reimbursements for already approved federal highway projects, and there is a danger that the Highway Trust Fund that serves as the main resource for repairs and maintenance may no longer exist after October when the new fiscal year begins.

Black stated that letting this fund dry up “would have a devastating impact on bridge repairs. It would set back bridge improvements in every state for the next decade.” Black assigned responsibility for the deterioration of the country’s bridges to federal budget cuts. “State transportation departments can’t just wave a magic wand and make the problems go away,” she said.

Since 2000, at least 16 bridges have failed in the United States, resulting in 31 deaths and at least 158 injuries. The most devastating failure was the 2007 collapse of the I-35W bridge in Minneapolis during bumper to bumper rush hour traffic. The collapse killed 13 people and injured 145 more.