SPRINGFIELD, Ill. (AP) — An Illinois advocacy group is looking to determine the impact of the state transportation lockbox amendment more than a year after voters approved the measure.

The State Journal-Register reports that nearly 80 percent of voters in 2016 approved the Safe Roads Amendment, which committed gasoline tax money and related fees to road and bridge construction projects.

Mike Sturino is president and CEO of the Illinois Road and Transportation Builders Association. He says the group is reviewing state budget proposals to see how transportation revenue is being used.

The association is part of a group of construction and engineering organizations that filed a lawsuit earlier this month against Cook County, alleging the county violated the amendment by diverting $250 million in transportation taxes to other expenses.