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  • Writer's pictureRachel Timokhina, CP&Y Blog Writer

I-35 Capital Express Program: South

From SH 71/Ben White Blvd. to SH 45SE in Austin, I-35 Capital Express South (colloquially known “CapEx South”) is part of a larger mobility initiative to improve I-35 led by the Texas Department of Transportation (TxDOT). CapEx South spans 9 miles of the total 28-mile corridor, which is divided into three segments (North, Central and South). As this portion of I-35 swings near the state capital, the interstate becomes one of the top 100 most congested roadways in Texas.** It was also the largest single let Design/Bid/Build project in TxDOT history!

Involving over 200 individuals from 10 firms, this large design team faced unprecedented challenges on this complex project.

Image shows a simplified map of the I-35 corridor and surrounding roads passing by Austin, Texas. The map is divided into three parts: the North, Central and South portions of I-35. Text points out that all three sections create a 28-mile corridor with US 183 acting as a detour route for traffic through the Central portion

The Challenges

Limited ROW Acquisition

The client requested limited ROW acquisition, so CP&Y found a way to fit nearly all of the proposed improvements within the tight, urban corridor. The proposed improvements included the addition of two non-tolled managed lanes in each direction, intersection bypass lanes, and new shared-use paths. To solve this space issue, our design elevated the managed lanes for 2.4 miles from north of Stassney Lane to north of Slaughter Lane. We also eliminated five direct ramp-to-mainlane merges and improved the east/west connections over and under I-35. By raising the managed lanes for a portion of the CapEx South corridor, we eliminated the need for additional ROW acquisition in this area.


To allow traffic to detour on US 183 around construction for the final Central segment, the North and South segments of the I-35 Capital Express Program needed to open around the same time. To make this possible, TxDOT needed to align efforts for CapEx South with CapEx North.

CP&Y wrapped up the 100% submittal for CapEx South with plans completed in just 11 months despite the COVID-19 pandemic restrictions. Good subconsultant relationships, constant communication with everyone on the team including the client, a strengthened QC/QA process and innovative uses for existing software all contributed to CP&Y’s ability to meet this challenging design schedule.


Beyond minimizing ROW takes and providing our design in record time, CP&Y minimized unnecessary effort and even incorporated additional design enhancements outside of the original project scope – all within the project budget by shifting budget between team members on this dynamic project.

CapEx South: A Career Milestone

Achieving this project’s design within an impressive timeline for delivery and using budget-conscious alternatives would not have been possible without the combined efforts of nearly 170 CP&Y employees. CapEx South is truly one for the books! We are so proud of everyone’s hard work and would like to acknowledge the impact that this monumental project has had on those still in the early stages of their careers. Scroll through the quotes below to learn how the careers of our young professionals have been significantly impacted by this milestone project.


For More Information

If you have any questions, please reach out to Project Manager, Wade Lansdell Strong, PE, for more details about CP&Y’s involvement in the Capital Express program. Connect with him on LinkedIn or contact him by phone at 512.492.6804 or by email at


** Teas A&M Transportation Institute, "100 Most Congested Roadways in Texas",

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