Building the proposed Illiana Expressway would be a “misplaced investment” of transportation improvement funds, and it’s questionable whether the highway is needed, according to a report by the staff of the Chicago Metropolitan Agency for Planning.

The report, which CMAP’s board will consider at its Oct. 9 meeting, expresses doubts on whether the envisioned toll road would be financially feasible — potentially requiring cash-strapped Illinois to cover a bigger share of the cost.

Released Friday, the report recommends that CMAP’s board reject the Illinois Department of Transportation’s request to include the Illiana Expressway in CMAP’s comprehensive regional transportation plan, Go To 2040.

State transportation officials in Illinois and Indiana have said the tollway would be built through a public-private partnership and is estimated to cost $1.25 billion, with Illinois’ share being $950 million.

The 47-mile highway would link Interstates 55 and 57 in Illinois with Interstate 65 in Indiana.

Residents who live in or near the proposed path of the tollway have been vocal in their opposition to the project, and three environmental groups — Openlands, the Midewin Heritage Association and the Sierra Club — filed a federal lawsuit to try to block the tollway.

CMAP staff note that Go To 2040 puts a heavy emphasis on modernizing and expanding capacity on existing roads and rail lines rather than “building expensive new projects that may be difficult to finance, operate and maintain over the long term.”

The 19-page report describes the Illiana Expressway as being “broadly incompatible with the overall goals and recommendations of Go To 2040” and that the method for financing the highway “remains uncertain.”

While it’s expected that tolls paid by cars and trucks using the Illiana would, over time, repay the private investment and also cover ongoing maintenance costs, CMAP staff suggest that there could be a funding gap of as much as $1 billion over the life of the tollway.

The report says IDOT’s estimate of the project’s cost “falls short of other comparable projects built recently both regionally and nationwide,” and that “the information provided to justify the project’s financial viability has been incomplete and largely anecdotal.”

Also called into question is one selling point of the Illiana Expressway that transportation officials and Gov. Pat Quinn have stressed — that the tollway would alleviate traffic, particularly heavy truck traffic, on Interstate 80.

Even if it were not a toll road, the Illiana would do little to relieve that congestion, and imposing a toll might “divert as much as 40 percent of the potential traffic” from the new expressway, according to the report.

CMAP’s board and another governing agency, the Metropolitan Planning Organization, ultimately decide how federal funds for transportation projects in the Chicago area are disbursed.

Prior to the board vote, CMAP’s transportation committee will consider the staff’s recommendation when it meets Friday.

Should that committee and CMAP’s full board reject IDOT’s request, the Metropolitan Planning Organization’s policy committee, headed by IDOT Secretary Ann Schneider, is set to vote Oct. 17 on the issue.