Illinois lawmakers have cleared a path forward for a long-discussed expansion of I-55, despite concerns from neighbors and environmental groups about the way the project could be funded and the repercussions of adding more lanes to the expressway.

In the final weeks of the legislative session, lawmakers moved to allow the Illinois Department of Transportation to pursue a public-private partnership to complete an expansion of I-55. Such a partnership, which would allow private investment in proposed new toll lanes on the expressway, is one way IDOT could secure funding to move the project forward.

Any new toll lanes along I-55 would likely be years away. IDOT previously completed studies of the proposed expansion, but officials said in a statement Friday the agency was not pursuing plans for the expansion at this time. The agency would be reviewing the legislation and evaluating next steps, they said.

The proposed expansion could include adding express toll lanes to the highway, which runs through part of Chicago’s Southwest Side and on toward Joliet. The concept calls for adding two toll lanes to each direction along an eastern section between I-294 and the exit ramps for I-90 and I-94, and a western section between I-294 and I-355 would get one additional toll lane in each direction.

Ed Maher, spokesman for the International Union of Operating Engineers Local 150, which represents construction workers and heavy equipment operators, said adding lanes to I-55 is sorely needed. Commuters need to be able to get downtown efficiently, and moving freight across the area quickly and easily is key to the region’s economy, including to the large intermodal facilities in Joliet.

“We’ve never been shy about voicing the need for safe and efficient infrastructure,” he said.

But environmental groups and organizations from some of the Southwest Side communities along the expressway oppose an expansion through neighborhoods where residents already have concerns about air quality. At a news conference before the resolution passed, opponents said additional lanes would add traffic, worsen pollution and increase the output of asphalt plants in the city that have spurred odor and air pollution complaints from neighbors.

“It’s a huge disappointment in our leadership,” José Acosta-Córdova, senior transportation policy analyst at the Little Village Environmental Justice Organization, said Friday. “They’re prioritizing economic development over the health of our communities along I-55.”

Little Village residents struggle with bad air quality, especially from particulate matter such as dirt or soot, and the expansion of I-55 will make the problem worse, he said. And, with widespread use of electric vehicles still far off, the potential for increased greenhouse gas emissions from additional vehicles in the new lanes seems counterintuitive to efforts to combat climate change, he said.

Rather than an investment in an expressway, Acosta-Córdova would like to see investment in public transit. The Southwest Side has CTA train access only via the “L” Orange Line, and better public transit could help reduce highway traffic, he said.

As the legislature gave approval to IDOT to pursue a public-private partnership, a bill also passed both houses that would change rules around public-private partnerships for transportation projections. Kevin Brubaker, deputy director of the Environmental Law and Policy Center, said the changes could lead to more of what he described as “boondoggles,” allowing a slew of new private-investment transportation projects in the state without requiring a planning agency to determine whether they’re necessary.

An expansion of I-55, meanwhile, will increase air pollution that disturbs neighboring communities and causes climate change, but won’t make drivers’ experience on I-55 any less frustrating, he said. Adding lanes to the highway will only increase its use, he said.

“You simply cannot build your way out of congestion,” he said.

sfreishtat@chicagotribune.com