I-35 rebuild through Austin starts with 51st St roundabout.

A computer generated rendering, promoted by TxDOT, shows a smooth flowing I-35 at 51st street. 

A roundabout intersection, along the southbound lanes, is a major part of the $16.5 million project.

The design is not an attempt to be “Austin weird,” according to TxDOT Austin District Engineer Terry McCoy. "It is a tried and proven method. Like I said, we looked at several different alternatives, several different configurations, predicted what the benefits would be of each, and this one was a clear winner for this location,” said McCoy.

TxDOT predicts traffic capacity at the intersection will increase by 30 to 50%. With no traffic lights, it’s anticipated the roundabout will shave four minutes off the commute through it. Crashes may be reduced by 35%.        

With the Wednesday ground breaking ceremony, construction will now get underway.

Completion is targeted for early 2019.

"A few minutes here, a few minutes there, we're making a difference in people's lives,” said State Senator Kirk Watson ( D) Austin.

There is also a south Austin part to the ground breaking. Work is also getting underway building a new overpass at Oltorf as well as widening the interstate, south of the river, between Woodland and Woodward St.

That project has a $42 million price tag.

All the construction equipment eventually will be moved down into the city core. But TxDOT officials say construction on I-35 there will not take place until all the work is done on MoPac and the 183 south projects known as the Bergstrom Expressway. There's a lot of work still to be done on those roads.

Austin Mayor Steve Adler seemed confident the critical east and west side by-passes will be done before construction begins downtown. "I look at MoPac and I’m told there is light at the end of the tunnel and it’s not a train,” said Adler.

Road builders acknowledge Austin is facing a decade long interstate make over. Its part of a statewide campaign called Texas Clear Lanes. Texas Transportation Commissioner, Bruce Bugg, said the effort is funded in large part by money siphoned out of the Rainy Day Fund. "It’s aspirational, it’s big in scope, but Texas is big and our problems in our five major metropolitan cities are big, it takes big dollars to attack big problems."

Austin is getting almost $160 million to kick off this new round of construction projects.

Funding for the next step - through downtown- has not yet been allocated -- which is why a firm start date has not been announced. The goal is to start the massive rebuild of I-35, between the river and Airport Blvd, four years from now.