Input sought for MoPac intersection proposal

"We are getting toward the end of the study," she said.

The scope of the projects proposed as part of the study—which include an innovative intersection design called a diverging diamond interchange, or DDI—is based on analysis and community input, Hurst said. A no-build option is also slated to be proposed.

In April or May the Mobility Authority plans to debut its schematics for the DDI at Slaughter and offer residents a final chance to share input as part of a public hearing and comment period, she said.

Afterward the Mobility Authority will submit an environmental assessment to the Federal Highway Administration for approval. Construction can only occur if it is approved, Hurst said.

Examining intersections

Where Slaughter meets MoPac, red tail lights are often illuminated one after the other as drivers inch forward to form a line while awaiting a green signal. The intersection was built in 1992, so it looks like most Austin intersections, Mobility Authority Engineering Manager Sean Beal said.

"We're looking at three different signal phases," he said, explaining the intersection's design is such that one group of vehicles can progress through the intersection at a time, followed by a second group, and then a third.

Transforming that intersection into a DDI design would add new main lanes to MoPac and reroute existing lanes on Slaughter in a way that would remove one of those phases from the equation, therefore improving traffic flow, Beal said.

Understanding a DDI without seeing it can be confusing, Beal admitted, noting construction on a DDI intersection recently began in Round Rock at I-35 and University Boulevard.

"When these [intersections] have been opened to traffic, our engineering community has been actually surprised by how quickly drivers figure it out and how intuitive it tends to be when you're driving it," he said.

Beal said signage and striping will provide clarity to drivers and enhance safety.

Bike and pedestrian improvements, such as sidewalks and crosswalks, will be incorporated, Hurst said. Cyclists would have a lane across Slaughter for a safe east-to-west connection.

Main lanes will also be added to MoPac at the La Crosse intersection, which will operate much like others in Austin, Hurst said.

Rubber meets the road

The project cost—an estimated $45 million, according to TxDOT—is a concern for Jason Bram, past Circle C Homeowners Association president and seven-year HOA board member. He said he is not sure if he is in favor of the DDI project but thinks overall, construction is needed to prevent crashes and allow development.

"There are some people that are for it [and] there are people that are against it, but we've had a lot of accidents and even a fatality at La Crosse [and MoPac]. So I am mainly in support of it because of the safety of our residents and the safety of the drivers in that area," he said.

In November the HOA replaced shrubs at the Slaughter intersection with rocks in an effort to give drivers a better line of sight, said Bram, who works as a tolling product specialist.

TxDOT also completed scheduled repairs in November to the Slaughter and MoPac intersection, repaving and restriping Slaughter to designate a right-turn lane for westbound Slaughter traffic turning onto northbound MoPac, TxDOT spokeswoman Kelli Reyna said.

Michael Portman co-owns Austin-based business Birds Barbershop, which opened its sixth location at MoPac and Slaughter in January. He said he is glad the intersection study is underway.

"To turn into our property when [traffic] is so stacked up like that can be challenging, so to relieve that in any way would be great. ... I don't know if this project is going to alleviate those problems so much as it will facilitate the future growth."

Portman said he hopes construction does not hurt area businesses by deterring drivers from taking those roads.

DDIs can prevent bottlenecks, said Southwest Austin resident Becky Bray, who ran for the Austin City Council District 8 seat and is a transportation engineer.

"Some of these designs [can] have a [smaller] footprint, [and] they don't require as much elevated structure," she said.

The increase in single-family units in the area has increased traffic congestion on MoPac at La Crosse and Slaughter, she said. The proposed project is one of many in Southwest Austin, such as SH 45 SW, that some residents want completed, Bray said.

"Anything we can do to facilitate the movement of people in an easier way, I'm a huge proponent of," she said. " ... The gridlock down there is just horrendous."

TxDOT estimates construction would take two years, Reyna said.

Hurst said there are no guarantees when construction on the project would begin.