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Setting Trends in Texas – the I-35 at 51st Roundabout in Austin, TX

The I-35 at 51st Street roundabout, the first of its kind on a Texas interstate frontage road, is making quite the impression on Travis County drivers and pedestrians alike.

In 2014, the Texas Department of Transportation (TxDOT) began studying a way to enhance mobility and safety on this segment of I-35, which was ranked third on Texas A&M Transportation Institute’s Top 100 Most Congested Corridors in Texas list and served several large-scale developments. Traffic data also showed that the area was popular for bicyclists and pedestrians. At the time, there was a high number of pedestrian fatalities and crashes, and the project area included many pedestrian destinations.

Early planners saw the I-35 at 51st Street project as not only an opportunity to improve mobility for vehicles, but also to update bicycle and pedestrian facilities along the east and west 51st Street corridor, which was anticipated to continue growing with ongoing redevelopment and expansion.

Using information from the 2014 Texas Strategic Highway Safety Plan, the project team began to evaluate a roundabout. These intersections are recommended to improve intersection safety and reduce overall crashes by 35% when compared to other types of intersection control. Roundabouts also result in fewer vehicle and pedestrian conflict points.

To gather input, TxDOT conducted a charrette with surrounding neighborhoods, including city partners and citizen groups focused on bicycle and pedestrian enhancements. Topics discussed in the charrette resulted in multiple benefits for the project, including a continuous north/south shared-use path between US 290 and Airport Boulevard; east/west connectivity across 51st Street; raised crosswalks with splitter islands and flashing beacons; and additional buffer zones. The innovative intersection design also allowed the project team to use the existing 51st Street bridge as is—resulting in significant cost savings for the project—and to include a southbound intersection bypass lane underneath 51st Street, as well as reconfigured entrance and exit ramps.

The $16.5 million project opened to traffic in June 2018, providing immediate mobility benefits.

Data shows that morning frontage road traffic traveling east across I-35 at 51st Street moved more than three times faster than before the roundabout opened, and traffic using the new intersection bypass lane began moving five times faster than it did going through the signalized intersection.

The I-35 at 51st Street project was the second Texas Clear Lanes project to open in Texas and the first in Austin. The Texas Clear Lanes program addresses Texas’ most congested highways, using funding from Proposition 1, approved in 2014 by 80% of Texas voters, and from Proposition 7, approved by 83% of Texas voters in 2015 for non-tolled transportation projects.

The I-35 at 51st Street project also included the largest investment in bicycle and pedestrian upgrades for an I-35 project to date. In addition to the Texas Clear Lanes funding, the City of Austin invested $9.2 million in the project, which helped pay for the pedestrian and bicycle upgrades.

It looks like going around in circles isn’t a time waster after all!