IH-35 Williamson County Expansion – Texas Department of Transportation

Austin County Texas

LAN performed the schematic and preliminary engineering for a transformative 6.5-mile stretch of Interstate Highway 35 from Round Rock to Georgetown, Texas. This project was pivotal in enhancing the efficiency and safety of one of the region’s most critical transportation arteries, paving the way for sustained economic development and mobility.

At the heart of this initiative was the development of a conceptual schematic designed to reimagine the highway’s infrastructure. The schematic introduced five key interchanges, each tailored to optimize traffic flow and improve accessibility:

  • Single-point urban interchange (SPUI) at SH 29
  • Diamond interchange at RM 2243
  • Fully directional interchange at the Georgetown Inner Loop
  • Displaced left at Westinghouse Road
  • Diverging Diamond at RM 1431

Key to the project’s success was the planning of managed lanes, main lanes, ramps, collector-distributors, frontage roads, and cross streets. LAN’s strategic approach included detailed calculations to ensure ample weaving distances—over 2,000 feet between main lane entrance and exit ramps, and over 1,500 feet between exits to frontage roads and entrance ramps, significantly enhancing the roadway’s safety and operational efficiency.

Moreover, the forward-thinking design anticipated future main lane expansions, carefully configuring corridor geometrics to avoid the need for costly and disruptive infrastructure modifications. This foresight minimized direct connector column and retaining wall replacements and significantly reduced right-of-way (ROW) takings. LAN’s approach not only preserved the community by avoiding displacements of residents or businesses but also aligned closely with the project’s goals of meeting capacity needs and supporting future growth.

At a glance

Schematic and preliminary design

5 mile highway expansion

Innovative interchanges

Multi-modal design


Displaced left turn

Partial cloverleaf

Tight urban diamond


Schematic Design


Texas Department of Transportation