Building the Illiana Expressway would help steer trucks off local roads and cut travel time from southern Lake County to some Illinois destinations by a third or more, according to a much-anticipated study of the proposed bi-state highway.

The Illiana Expressway Feasibility Study, commissioned two years ago by Indiana and Illinois, offers a detailed look at the possible impacts of a 25-mile expressway running from Interstate 65 to Interstate 57 on other region roads.

The Illiana Expressway's supposed role as a reliever for other area roadways always has been cited by proponents as a powerful argument for building it.

But in one of the report's more surprising findings, the proposed east-west highway would siphon only about 2.2 percent of traffic from the oft-congested Borman Expressway. Natural increases in traffic will put about 199,000 cars and trucks per day on the Borman by 2030, according to the study. That's compared to about 155,000 vehicles per day in the state's most recent traffic maps.

"We who live in the northern part of the Lake County are well aware of what a nightmare it can be to drive on U.S. 41 and (U.S.) 30 and the Borman Expressway," said state Sen. Earline Rogers, D-Gary.

Rogers is a member of a legislative committee that will be briefed on the report this summer.

According to the study by transportation consultant Cambridge Systematics, heavy trucks would spend anywhere from 9 percent to 16 percent less time on local roads if the Illiana Expressway is built.

Mainly, that's because the expressway would offer a speedy route to destinations in the fastest-growing sections of Lake County, Indiana, and Will County, Illinois.

The Illiana Expressway could shave about one third of the time off a trip to fast-growing Will County for residents of South Lake County, according to the study.

It also would pull off about 7.5 percent of cars and trucks on U.S. 30 east of U.S. 41, which is one of the road's most congested sections as it heads out of Schererville and passes through Dyer.

But traffic on portions of U.S. 41 actually would increase, mainly because one of only two proposed Illiana Expressway interchanges in Indiana would be located there. That interchange would increase traffic on U.S. 41 just north of the Illiana Expressway by about 35 percent.

Up to 35,500 vehicles a day could be using the Illiana Expressway by 2030, according to the report. Scenarios have it run as a toll road, with the cost of the full 25-mile trip ranging anywhere from $2 to $6 for a car and from $7 to $21 for a semi-trailer.

Most of the projected traffic counts were done for a northerly route starting at Interstate 65 just south of U.S. 231 and skirting the north side of Cedar Lake before reaching Illinois. There are two other proposed routes farther south.

The report was commissioned by Indiana and Illinois, with proponents of the Illiana Expressway hoping it would kick-start building of the road. In Indiana, it was authorized under legislation passed by the General Assembly two years ago.

There is no surprise that the study predicts building a major expressway like the Illiana could have wide-ranging effects on traffic patterns throughout the region, according to Steve Strains, deputy director of the Northwest Indiana Regional Planning Commission.

Getting truck traffic off local roads is always a positive and a key concern when planners look at how to improve regional transportation, Strains said. The study done by Cambridge Systematics will be a part of NIRPC's considerations as it plots the region's path forward in its new 2040 Comprehensive Regional Plan

Illiana Expressway: to build or not to build?

Here are some of the projected traffic counts for selected portions of area roadways by 2030 with and without the Illiana Expressway.

Borman Expressway

With: 193,853

Without: 198,310

Difference: 2.2 percent decrease

U.S. 30

With: 27,768

Without: 30,021

Difference: 7.5 percent decrease

Interstate 65 at Illiana Expressway

With: 45,269

Without: 39,481

Difference: 14.7 percent higher

Source: Illiana Expressway Feasibility Study