What’s a ‘cap and stitch?’ Austin eyes traffic technique to improve I-35 mobility


AUSTIN (KXAN) — How does Austin reconnect its eastside with downtown and improve non-vehicle mobility? Those are two guiding questions behind a proposal the city and Downtown Austin Alliance are pursuing as part of the upcoming Interstate 35 reconstruction project.

The Texas Department of Transportation is in the process of tackling a $4.9 billion I-35 revamp along a 10-mile stretch through central Austin. Running from U.S. 290 East to SH 71 and Ben White Boulevard, the Capital Express Central Project aims to tackle congestion issues related to the roadway.

Key features in the proposal include removing the upper decks along I-35 and lowering the highway between Airport Boulevard and Cesar Chavez Street. Several grassroots-led plan alternatives, including ReThink35 and Reconnect Austin, have denounced TxDOT’s proposed widening of I-35 and subsequent displacement of homes and businesses.

While city leaders have noted a collaborative process with TxDOT representatives, city transportation officials have outlined key amendments they’re looking to see implemented following TxDOT’s initial project proposal. These include enhancing east-west connectivity, non-vehicle mobility and the history of segregation between the eastside and downtown corridor via I-35 — all elements the DAA’s “caps and stitches” proposal hopes to address.

“The Downtown Alliance is invested in the outcome of the I-35 reconstruction project to ensure that it not only reunites the east and west sides of our city and enhances environmental and health outcomes, but also offers the mobility solutions and congestion relief our city needs,” Dewitt Peart, DAA president and CEO, said in a statement. “There is much to like in TxDOT’s current plan, but there is also room for improvement. The time is now for the City of Austin, TxDOT and our community to work together if we want the benefits of a lowered, safer, healthier, more multi-modal supportive, and therefore, a more equitable I-35.”

What’s a cap and stitch?

Caps are deck plazas that run north to south on top of lowered freeways. As part of the designs, caps can support buildings, green space and other community attractions.

The city of Austin and Downtown Austin Alliance have proposed a cap and stitch solution to addressing east-west connectivity and mobility as part of the upcoming I-35 revamp. (Courtesy: Downtown Austin Alliance)

Through the city’s recently approved Climate Equity Plan, Austin has established a 2050 goal of having a minimum 50% tree canopy coverage citywide. A report released by the conservation nonprofit American Forests in June found a 20% disparity in tree canopy coverage between Austin’s high-income and low-income neighborhoods.

Stitches are defined as widened bridges stretched over lowered highways that run east to west. Stitch features include widened sidewalks, bike lanes, seating areas and green space.

Stitches are widened bridges on top of lowered highways that can support bike paths, sidewalks, seating areas and green space. (Courtesy: Downtown Austin Alliance)

DAA officials note a reduction in noise pollution related to the green space, while widened sidewalks and designated bike paths help support non-vehicular mobility and east-west connectivity.

Also as part of Austin’s Climate Equity Plan, the city highlighted a 2030 goal related to enhanced non-vehicle transit. By 2030, Austin aims to have 50% of all trips made in the city be done via public transit, walking, biking, carpooling and other modes that don’t include single-occupancy vehicles.

“The Downtown Alliance is invested in the outcome of the I-35 reconstruction project to ensure that it not only reunites the east and west sides of our city and enhances environmental and health outcomes, but also offers the mobility solutions and congestion relief our city needs,” DAA president and CEO Dewitt Peart said. (Courtesy: Downtown Austin Alliance)

How do caps work?

Designs on top of caps are dependent on how much load the structure can withstand. With TxDOT’s I-35 reconstruction project, the city’s hope is that caps are built concurrently with other infrastructure improvements, said Mike Trimble, director of the corridor program office.

Neighboring examples of caps include Klyde Warren Park in Dallas, which includes green space and event space on top of the highway.

“You really don’t know that a highway is underneath it. And that really is what we’re seeking with this,” Trimble said. “And so it achieves a lot of objectives. It can help with air quality, providing more green space. It can provide better connectivity, a safer environment for folks to interact between east Austin and downtown.”

Trimble said his office is trying not to be presumptive about what specific amenities will be included in the caps, should the proposal but greenlit; instead, he said he wants to collaborate with community members on what uses they want highlighted.

Addressing I-35’s segregation

In city and community dialogues surrounding the project, the history of I-35’s segregation as a physical barrier disconnecting the eastside from downtown have been noted. Prior to I-35, East Avenue operated as an extensive boulevard.

“I-35 has really been kind of the symbolic and physical dividing line between east and west Austin. It was East Avenue, and it was an important connection point for our Hispanic and black communities in the 1900s, in the 20th century. And then as the highway was built, that just, it kind of doubled down on the on the division and the segregation in our community.”

mike trimble, director, city of austin’s corridor program office

As the city has reviewed TxDOT’s proposal, officials said they are working to incorporate amendments that help make amends for decades of division. Trimble said the east-west connectivity and community space offered via the cap and stitch proposal could help address that.

“We want to really work with the community to figure out what this will look like,” he said, adding: “We really want to do that collaboration and in conjunction with the community.”

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