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.

In 2016, nearly 80 percent of voters approved the Safe Roads Amendment, which committed gasoline tax money and related fees to road and bridge construction projects.

A group of construction and engineering organizations 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.