"Cut and cap" – the idea of burying I-35 in the downtown corridor and paving over that chasm to create greenspaces or mixed-use development – is no longer in the rearview mirror.

Congress for the New Urbanism, a nonprofit transportation advocacy group, highlights the idea in a new study (grimly) titled "Freeways without Futures."

It’s an idea from Sinclair Black, a UT professor and architect, that first arose in 2013. It idealizes an I-35 that's receded below its current level and capped with 30 acres of concrete – similar to Klyde Warren Park in Dallas.

Black started the group Reconnect Austin to promote the plan as TxDOT considered how to reduce congestion on I-35 in downtown Austin – a road on which more than 175,000 vehicles traveled daily and spent more than 10.7 million hours in traffic delays in 2018, according to the Texas Transportation Institute.

Reconnect Austin's proposal would create a more narrow, more pedestrian-, transit- and bike-minded boulevard above the subterranean lanes of I-35.

Black says the reconfiguration would cut down on stop-and-go traffic by simply offering more options, tapping into the city's old grid.

"By civilizing the boulevard above, you are further slowing the traffic down, integrating it into essentially the original grid system of the city, and turning it into parks, open spaces and boulevards," he said.

Black says a buried I-35 would allow East and West Austin to reunite through that original grid system after decades of economic and racial separation in, at the very least, a symbolic sense.

The plan is a bit of a moonshot, but it has gotten support of city, state and county leaders in the past.

It's ultimately up to TxDOT, which owns the right-of-way to the land. A partnership of this magnitude isn't completely out of the question, though: The state's transportation agency partnered with the City of Dallas and private backers to bring Klyde Warren to bear. Still, that park is a fraction of the size of this proposal – 5.2 acres compared to 30.

TxDOT announced an $8 billion project to overhaul I-35 in late 2017, but – other than knocking down the double-deck between Airport and MLK, it’s unclear what that revamp would look like, or whether TxDOT would be open to Black's idea. If it did decide to partner with Austin on the project, the capping would still cost the city an estimated $300 million.