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Tell TxDOT What You Think About Expanding I-35 In South Austin

I-35 South looking north from Slaughter Lane.
Nathan Bernier
The I-35 Capital Express South Project includes a proposal to add four elevated lanes — two in each direction — from this point north of Slaughter Lane to Ben White Boulevard.

More than 150,000 vehicles per day, on average, drive the stretch of I-35 between SH 45 Southeast and Ben White Boulevard. The Texas Department of Transportation wants to make room for tens of thousands more.

TxDOT released the final version of its proposal to do this on Tuesday and is asking the public to give feedback on it over the next month.

The I-35 Capital Express South Project is a $300 million plan to add a pair of high-occupancy vehicle lanes in each direction along this 7.6-mile stretch of the interstate. TxDOT’s definition of a “high-occupancy vehicle” includes cars, pickup trucks and vans with more than one person in them. The lanes would not be tolled. The project is part of a larger plan to grow I-35 across Travis County.

Between Slaughter Lane and Ben White, TxDOT would add those extra four lanes by building an elevated roadway, an “upper deck” between the main lanes.

South of Slaughter Lane, the project imagines increasing the number of lanes from 10, including the frontage roads, to 18. A 10-foot wide path for pedestrians and cyclists would be added to either side.

The project would reconstruct bridges. Five on-ramps that merge directly into the main lanes of I-35 would be eliminated. Traffic noise barriers would be constructed along portions of the highway. TxDOT made a YouTube video showing the proposed changes:

TxDOT argues the project is necessary to maintain the economic livelihood of the city. Population and employment growth are contributing to increased congestion.

A traffic safety evaluation by UT Austin’s Center for Transportation Research found TxDOT’s plan to add an elevated roadway would reduce crashes by 28% compared to doing nothing.

Many people oppose the project.

Respondents to a 2019 public meeting cited concern over a phenomenon known as “induced demand,” in which drivers are lured to new highways only to result in the roadways eventually becoming congested once again.

Others were concerned about spending heavily on highways when transportation already accounts for almost a third of U.S. greenhouse gas emissions.

“We are also in a climate crisis,” pedestrian advocate Adam Greenfield told TxDOT in 2019. “How can TxDOT possibly keep going down this ruinous path?”

Other respondents opposed the project because it will increase the volume of traffic.

“Intensifying the amount of polluting high-speed traffic through the middle of a city is highly inappropriate because it is at odds with pedestrians, cyclists, health, and connected walkable communities,” Stephanie Scholten said.

The newest opportunity to submit comments to TxDOT on I-35 South started Tuesday. Feedback must be submitted by May 26 at 11:59 p.m. to be included in the public record. You can tell TxDOT what you think here. You can also leave a comment by voicemail at 512-501-5451 or email

Nathan Bernier is the transportation reporter at KUT. He covers the big projects that are reshaping how we get around Austin, like the I-35 overhaul, the airport's rapid growth and the multibillion dollar transit expansion Project Connect. He also focuses on the daily changes that affect how we walk, bike and drive around the city. Got a tip? Email him at Follow him on Twitter @KUTnathan.
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