In the years since Massachusetts received about $7 billion from the federal government for Boston's massive underground highway project known as the Big Dig, the state — like most others — has seen U.S. funding for transportation upkeep slowly diminish.

According to figures compiled by The Associated Press, money available to Massachusetts from the Federal Highway Trust Fund dropped 3.1 percent between the 2008 and 2013 fiscal years. Adjusted for inflation, Massachusetts has seen a 10.1 percent reduction in highway trust fund receipts over five years.

The loss of federal highway dollars adds to a transportation financing puzzle that has left commuters increasingly frustrated and policymakers groping for answers. The Legislature in its last session approved a 3-cent increase in the state gasoline tax, but legislative leaders say additional steps are likely needed.

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