(AP) Indiana and Illinois signed an agreement to build the Illiana Expressway toll road, with Indiana paying $80 million to $110 million, Illinois agreeing to pay at least $250 million, and the rest of the $1.51 billion for the project coming from private investors.

The 33-page document outlines the responsibilities of each state and how the 47-mile highway will be run. The agreement specifically states the road between Interstate 65 near Lowell in northwest Indiana and I-55 near Wilmington, Illinois, 60 miles south of Chicago, will be reserved for vehicles using electronic toll devices with no option for those wanting to pay cash. The road will be a four-lane highway that could later be expanded to six lanes.

The deal also specifies that each state is responsible for the design, financing, construction and operations of the highway in their state, with Illinois being responsible for the bridge at the state line. The agreement calls for the two states to have contracts for design, construction and operation and maintenance of the road by early 2015, and to use their “best efforts” to have the road completed by the end of 2018.

Illinois Transportation Secretary Ann Schneider issued a statement saying the deal will help the economies of both states.

“This agreement solidifies that partnership and our commitment to the success of this project,” she said. “Moving forward with our regional and local partners, we are not just building a road, but creating jobs, promoting economic development and improving mobility throughout the region.”

Critics argue that the road won’t have much of an effect on economic development and that it will harm the environment. Andrew Armstrong, a staff attorney of the Environmental Law & Policy Center that has filed two lawsuits trying to stop the highway, said the agreement highlights the financial risks to both states.

“This is a time of really uncertain funding levels at the state and federal level for transportation and there’s no need to build this project using very precious taxpayers funds when it’s going to be used by so few vehicles in comparison to the existing roads that need maintenance and upkeep,” he said.

INDOT spokesman Will Wingfield said the plan calls for private investors to pay the costs the states don’t pay and then to receive annual payments through the toll collections. Officials have said it could take up to 18 years for the tolls to start generating a profit. The agreement says Illinois will take 39 years to pay its share of the costs, while it will take Indiana 35 years to pay off its share.

The agreement estimates the cost of the highway to nearly $1.51 billion and says that figure could be changed after the environmental impact study is completed. Officials with the two states had earlier placed the estimated cost at $1.3 billion.

The states are still awaiting federal approval of the project.

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