The Illinois and Indiana departments of transportation, along with the Indiana Finance Authority, have signed an agreement to build the proposed Illiana Corridor.

The 47-mile, east-west route toll road will connect Interstate 55 near Wilmington, Ill., about 60 miles southwest of Chicago, and Interstate 65 near Lowell, Ind., in the northwest part of the state.

The agreement, signed last month but not made public until this week, outlines each state's roles, responsibilities and project management duties, as well as project delivery requirements and schedule. Indiana will pay up to $110 toward the project with Illinois contributing up to $250 million. The rest of the more $1.5 billion will come from private investors, according to published reports.

The goal is to have the route completed by the end of 2018.

"This historic partnership between Illinois and Indiana will pay dividends to the economies in both states," said Illinois Secretary of Transportation Ann L. Schneider. "This agreement solidifies that partnership and our commitment to the success of this project. 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 say the route will do little in the way of economic development and could take both states many years to see a profit on building the highway.

The route still needs approval by the federal government and faces at least two court challenges.