BANGOR – Despite increased efforts at modernization, a third of Maine’s state-maintained roads fail to meet national standards, according to a study released Wednesday by a transportation research group.

The study, performed by The Road Information Program, or TRIP, also found that one out of seven, or 14 percent, of state-maintained bridges are structurally deficient with visible signs of deterioration.

TRIP, a national nonprofit organization funded by insurance companies, labor unions and the construction industry, performed the study at the request of the Maine Better Transportation Association.

The report comes as federal transportation legislation under the Transportation Equity Act for the 21st Century is due to expire on Sept. 30 and passenger and commercial truck travel on Maine roads increases.

Improvements have been made since the original Transportation Equity Act for the 21st Century passed in 1998, the report said. At that time, 40 percent of Maine’s state-maintained roads were substandard, compared with 33 percent today. The report also said that 17 percent of bridges were structurally deficient in 1998, compared with 14 percent today.

“The ability to make continued modernization really depends on federal funding for transportation,” said Paul Haaland, associate director of policy and research for TRIP. “And a 35 percent increase in overall highway use is expected over the next 20 years.”

The Maine Department of Transportation projected minimal improvement to the highway system if current funding levels continue, while a 25 percent increase for the life of the legislation, through 2009, would allow for greater progress, according to Carl Croce, director of the DOT’s Bureau of Planning.

A 50 percent increase would allow for improvements to 576 miles of the state-maintained highway system, 170 percent more than with the current level of funding, according to the report. High-priority projects such as the Deer Isle-Sedgwick Bridge and the Calais border crossing could also be completed, Haaland said.

A new Route 1 bridge over the Penobscot River between Waldo and Hancock Counties will be built regardless of future funding levels, but a 50 percent increase would prevent siphoning money from other projects, Haaland said.

The role transportation plays in Maine’s economy requires such an allotment, according to Dana Connors, president of the Maine Chamber of Commerce.

“Already 86 percent of our commerce moves over our highway system,” he said. “It costs a lot to build and maintain a good highway system, but it costs a lot more not to.”