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SH 45SW Toll

Our team performed PS&E design services on this high-profile project that involved four bridge widenings, two new overpasses, a 1247-foot-long stream crossing at Bear Creek, a 100-foot bridge over a karst feature, and four direct connectors at the intersection of SH 45 and Loop 1.

The project evolved from efforts beginning in the early 1980s to create a controlled-access highway facility (called the Austin Outer Parkway) circling the City of Austin. State Highway 45SW Toll is located within what was previously known as Segment 3. Even though the Austin Outer Parkway is no longer being pursued, the 45SW project remained a priority for the community to improve system connectivity, local mobility, and travel times while providing an efficient alternative route to congested local roadways in northern Hays and southern Travis Counties, which are areas with limited controls in place to protect water quality and sensitive features.

TxDOT launched an Environmental Impact Statement (EIS) in June 2013 to study possible solutions, resulting in the recommendation to construct 45SW, a new four-lane toll road on existing state-owned right-of-way from MoPac to FM 1626. After TxDOT issued a Record of Decision in March 2015, RTG (Prime) led the design effort for the Central Texas Regional Mobility Authority (CTRMA) to incorporate concepts from CTRMA’s Green Mobility Challenge and Context Sensitive Solutions initiatives. The team refined and implemented unique, innovative design concepts, identified during the schematic phase, through design and construction of one of Austin’s most environmentally sensitive projects.

For 45SW, the design team implemented state-of-the art water quality protection measures, which exceeded the State’s regulations for controls on TxDOT projects. A shared use path (SUP) provided both connectivity between the northern and southern segments of the Violet Crown Trail (a planned, 30-mile trail extending from Central Austin into Hays County), as well as additional water quality mitigation efforts by building the SUP above the natural ground to create a berm that separated offsite runoff from roadway runoff. Mitigation efforts to avoid over 20 sensitive karst features, including Flint Ridge Cave (the 5th largest cave in Austin), resulted in a roadway right-of-way-characterized by some as a “transportation conservation landscape.” The mitigation efforts were recognized by local stakeholder agencies as a model for future sustainable highway development in the region.

Services Provided:

  • PS&E Design Services

  • Structural

  • Environmental

  • Drainage

Project Highlights


Central Texas Regional Mobility Authority/Texas Department of Transportation - Austin District


Austin, Texas


Your contribution in moving this important and challenging project
through the environmental process is much appreciated. I also want to pass along the appreciation of the TxDOT leadership.

- Carlos Swonke, TxDOT Environmental Affairs Division (Retired)



4 Miles

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