With more than 150,000 vehicles moving through Round Rock on I-35 each day, Texas Department of Transportation and city officials aim to reduce the number of bottlenecks and improve travel times in the area.

A new project at FM 3406 and I-35, listed as one of the top 100 most congested roadway segments in Texas, according to TxDOT, will cause some headaches before it gets better, officials concede.

“There will be a little bit of pain with this project,” Round Rock Mayor Alan McGraw said at Tuesday morning's groundbreaking ceremony for the four-phase project. “In the end, [FM] 3406 will be better for everybody.”

The $12.4 million project will replace and widen the Old Settlers Boulevard bridge; construct two new U-turn bridges, one in each direction; and make bicycle and pedestrian enhancements within the project. Work is expected to be complete by spring 2019, weather permitting. Road closures will be announced. Lane closures will be common, officials said.

Here is a breakdown of each construction phase:

• Phase I includes making improvements to the center median and drainage on I-35 under the existing bridge.

• Phase II work includes constructing retaining walls near Old Settlers Boulevard, demolishing and rebuilding the south half of the bridge, constructing the new northbound and southbound bridge, and performing the frontage road work.

• Phase III work includes shifting traffic to the new Old Settlers Boulevard bridge and demolishing and rebuilding the north half of the bridge, constructing the new southbound to northbound turnaround bride and performing frontage road work.

• Phase IV work includes completing construction of the median on Old Settlers Boulevard as well as performing final paving operations for the entire project.

Kevin Dickey, TxDOT Austin Deputy District engineer, said the project will have strong partners in the city of Round Rock and Flatiron Constructors Inc.

“We’re turning I-35 into a smart, efficient highway, and this is a positive step forward,” Dickey said.

Flatiron Constructors Texas Region Operations Manager Joe Schroeder promised a safe and effective project, “on time and under budget.”

McGraw said he’ll be affected by the project, along with thousands of travelers.

“When they opened I-35 in the 1950s, they said they built it to its ultimate capacity,” McGraw said, as attendees laughed. “I think they missed it a little.”

TxDOT will announce road closures as needed. The Round Rock Fire Department and Williamson County are looking at staffing a temporary station with a fire truck and ambulance on the west side of the intersection.

As far as alternative routes, TxDOT said the westbound access over Old Settlers Boulevard will not be completely cut off. Traffic headed east will be diverted south on the I-35 frontage road to the U-turn at Hwy. 79, and then north on the I-35 frontage road back to Old Settlers Boulevard. Additional alternative routes would be to take Chisholm Trail south to Sam Bass Road or to take RM 1431 to Sam Bass Road, down to Creek Bend Boulevard, over to Wyoming Springs Drive, down to RM 620 and back to I-35.