The Texas Department of Transportation will finish a yearlong study in January to analyze the best use of adding two lanes to I-35 in Travis County.

The agency would add one lane in each direction on I-35 from SH 45 N to SH 45 SE, dubbed the Future Transportation Corridor. The FTC would also extend throughout Hays and Williamson counties as part of TxDOT's Mobility 35 program designed to improve I-35 congestion.

"I-35 is the most congested corridor in Texas in downtown Austin," said Terry McCoy, TxDOT deputy district engineer for Austin. "[The FTC] will address congestion and provide more reliable travel times."

TxDOT began a Planning and Environmental Linkage study in early 2014 to analyze the purpose and need of the FTC and to determine the best type of lane to use, such as general purpose or toll lanes.

Two preferred alternative lane types that surfaced during the study are managed toll lanes, similar to the lanes being added to MoPac, and managed toll lanes with a transit focus. The latter alternative would also provide direct access to Capital Metro Park & Ride facilities for buses. McCoy said these two options provided the most efficient way to manage traffic and improve travel times in the main lanes. View the presentation of the alternatives here.

The cost of building the FTC is about $5 billion, McCoy said.

"We've got a lot of operational improvements that go along with FTC," he said. "That's just one part we're doing. All of the auxiliary lanes, ramp modifications, intersection and frontage road improvements—that's included in the $5 billion."

Once the study wraps TxDOT will complete an environmental study of the two alternative lane types. Those could take two to three years to complete, and TxDOT has set aside about $4 million for the environmental study, McCoy said.

TxDOT is also continuing public meetings in both Hays and Williamson counties to present mobility improvement projects to the community. Those meetings will finish in January, and TxDOT will then take its plans for Hays and Williamson counties through the environmental process. McCoy said a PEL study is not required for those two counties's portion of the FTC.

For more information visit www.mobility35.org.