AUSTIN (KXAN) — In the near future, Interstate 35 through downtown Austin will undergo a complete transformation, but for now, the Texas Department of Transportation is starting in south Austin.

Here are the changes coming for I-35 from State Highway 45 southwest to Highway 71. TxDOT will begin construction on Tuesday.

It will be putting in two non-tolled high-occupancy vehicle lanes in each direction along I-35. Plus you’ll see improvements to the east/west connections, and TxDOT will add about 13 miles of new shared-use paths.

Though the interim will be rough as any major construction project is, when it’s all said and done it will help keep traffic moving.

The I-35 Capital Project South will cost $548 million and is expected to wrap up in late 2028.

The I-35 Capital Project overall includes downtown Austin, where we could see the removal of the upper/lower deck split, more lanes, buried lanes and a huge undertaking expected to start in 2025.

This includes the north side of Austin from Highway 290 to SH 45, which should start next year.

Lawsuit filed against TxDOT

Three groups on Friday called for an immediate halt to the project plan.

The Texas Public Interest Research Group (TexPIRG), Environment Texas, and Rethink35 filed a lawsuit in June against TxDOT over its broad plan of expanding a portion of I-35 that stretches from north of Buda to Round Rock.

“TxDOT must immediately pause the I-35 Capital Express South widening project while the judge considering our lawsuit decides whether or not this project can legally proceed,” says Luke Metzger, Executive Director of Environment Texas. “Proceeding nonetheless will be a bad faith act that will further diminish the community’s trust in TxDOT.”

The groups say that the environmental impacts of expanding the interstate are expected to be considerable. The entire expansion is expected to generate 255 million to 382 million additional vehicle miles traveled per year, according to an estimation by Grist. That would result in 1.2 to 2.6 million metric tons of carbon dioxide equivalent emissions by 2050, “roughly equal to the annual greenhouse gases generated by a small coal-fired power plant.”

The lawsuit alleges that splitting its massive I-35 Capital Express expansion project into three parts is an unlawful attempt to skirt public engagement and environmental impact assessment requirements.

The plaintiffs are calling for TxDOT to restart the entire project and build a proposal from the ground up with community members at the center of discussions.

KXAN reached out to TxDOT to ask if they had a statement, and they said they do not comment on pending litigation.