Maryland's transportation trust fund has been used for more than 20 years to balance the budget in tough times.

Since 1984, $574.1 million has been transferred from the transportation trust fund to the state's general fund, budget documents show. Of that, $544.3 million has been replaced.

However, that does not account for money transferred from the transportation trust fund to the state's "rainy day fund." Last fiscal year, Gov. Martin O'Malley transferred $100 million from the transportation trust fund -- $60 million to the general fund, scheduled to be repaid between fiscal 2014 and 2016, and $40 million to the rainy day fund, which is not scheduled for repayment.

It also does not account for money put in the general fund from revenue that typically goes to counties and local jurisdictions to pay for road maintenance. Since 2003, the state has transferred more than $1.1 billion from these revenues, none of which has been repaid.

Transportation advocates have been urging the state to put the trust fund in a lockbox, preventing the money from going to anything other than transportation.

"The governor and the state legislature ought to be taken to the woodshed for the way that they have failed," said AAA Mid-Atlantic spokesman Lon Anderson, who sat on a state panel commissioned with finding new transportation revenues last year.

But locking the money up would be a mistake, said Warren Deschenaux, director of the General Assembly's Office of Policy Analysis.

"In times where the economy is tanking, we need to be able to draw on the totality of state resources," he said. "We don't take money out of the transportation trust fund just because it's fun." - Rachel Baye