Stephanie Newhouse, a divorced mother of two in Pulaski, Tenn., had her license suspended for a time after a drunken-driving conviction in Georgia. She said that the suspension was fair punishment, but that having to pay hundreds of dollars to reinstate the license was not. Ms. Newhouse has been able to work only part time since the suspension because her hours are contingent on when she can get a ride to work at an insurance office two counties away.

“You really have to have a full-time, really good job to be able to pay it back,” she said.

Though the law was projected to raise more than $20 million a year, it has not come close, according to state agencies. Revenue from litigation taxes, the primary court fee collected by the state, has remained flat and even declined a bit in 2014, and license reinstatement fees have increased far less than was anticipated.

But since suspensions under the law began in mid-2012, almost 90,000 licenses have been suspended. Over the same period, 170,000 Tennessee licenses were suspended for unpaid traffic tickets. In both categories, more than 40 percent of the suspended drivers were black, compared with 16 percent of state residents.

Still, State Senator Jack Johnson, one of the sponsors of the 2011 law, said it was needed to rein in shirkers. “It’s usually not a tremendous amount of money; it’s just that folks are just blowing it off,” he said.

Mr. Johnson, a Republican from Williamson County, just south of Nashville, pointed out that the law gives people a year to pay and that it allows people to petition for a hardship license to get to work — a provision that some court officials, public defenders and even one judge said they were unfamiliar with.

“Not a single person has approached me about changing this,” Mr. Johnson said. “Every one of these people ending up with these court fines and fees and expenses, it’s as a result of violating the law in some capacity.”