Interstate 10–Loop 1604 interchange

The Interstate 10–Loop 1604 interchange, also nicknamed the Fiesta Stack, is a five-level stack interchange on the northwest side of San Antonio, Texas, where Interstate 10 meets Loop 1604. The structure is part of the Loop 1604 North Expansion Program, a multi-year effort led by the Texas Department of Transportation to improve mobility and reduce congestion along San Antonio's rapidly growing northern corridor. It serves as a critical junction linking local, regional, and long-distance traffic between San Antonio, Austin, and West Texas.
As of August 2025, the interchange’s tallest direct connector reaches approximately above grade, surpassing the 120 ft High Five Interchange in Dallas to become the tallest recorded highway flyover ramp in the state. The interchange is slightly lower than the maximum height of the Judge Harry Pregerson Interchange in Los Angeles, California.
Its design accommodates high-capacity movements between commercial, residential, and recreational destinations, including The Shops at La Cantera, The Rim, and Six Flags Fiesta Texas. It is considered one of San Antonio's most complex infrastructure projects due to its size, elevation, and phased implementation.

Design

The interchange utilizes a five-level Texas stack configuration intended to separate high-volume traffic flows between I-10 and Loop 1604. Each level is designed to minimize weaving and merging conflicts while supporting speeds up to on flyover connectors and on through lanes. Four high-speed, two-lane directional connectors carry the heaviest traffic movements, while auxiliary ramps provide access to adjacent interchanges and frontage roads. Beneath the elevated structures, TxDOT implemented a unique four-roundabout frontage road layout, informally referred to by project engineers as the "fidget spinner" design. The roundabouts were introduced to simplify turning movements and consolidate access points, which improves safety and reduces signal delays. Pedestrian and bicycle access was incorporated into the frontage system where possible, reflecting TxDOT's evolving multimodal design standards. Drainage upgrades, retaining walls, and noise abatement measures were also integrated into the layout to mitigate environmental and community impacts. The interchange's vertical clearance and flyover heights were engineered to accommodate projected freight demands, particularly with increased truck traffic associated with the I-35 and I-10 freight corridor. According to TxDOT traffic models, the final design is expected to accommodate up to 400,000 vehicles per day by 2040.

History

Planning for the interchange reconstruction began in the late 2010s as part of TxDOT's broader Loop 1604 North Expansion Program. At the time, San Antonio's northwest corridor experienced rapid residential and commercial growth, driven by developments such as The Rim, La Cantera, and the expansion of the University of Texas at San Antonio. Increasing congestion along I-10 and Loop 1604 made the existing cloverleaf interchange inadequate for projected traffic volumes. In 2019, TxDOT completed environmental assessments and preliminary engineering studies, determining that a five-level stack design would best meet long-term mobility needs. Funding for the project was secured through a combination of state allocations, federal grants, and local contributions via the Alamo Area Metropolitan Planning Organization. Public hearings and community input sessions were held between 2020 and 2021 to address concerns about noise, traffic disruptions, and property impacts. The final design balanced improved freeway-to-freeway movements with upgraded local access for surrounding neighborhoods. The project also aligned with long-term plans to expand Loop 1604 into a fully controlled-access freeway along its northern arc. As part of San Antonio's transportation infrastructure strategy, the interchange serves as a critical component connecting growth centers in northwest Bexar County to the regional highway network.

Construction

Construction on the Loop 1604/I-10 interchange began in July 2022, managed under TxDOT's multi-segmented North Expansion Program. The work was divided into several phases to minimize disruptions, with different contractors assigned to individual segments. The first phase focused on clearing right-of-way, relocating utilities, and building retaining walls to support the elevated connectors. Subsequent phases involved simultaneous construction of multiple flyover ramps, requiring precise sequencing to maintain traffic flow through the corridor. Phased openings began on December 3, 2024, with the completion of the Loop 1604 eastbound to I-10 westbound connector. The second connector, carrying I-10 westbound to Loop 1604 westbound traffic, opened in May 31, 2025, followed by the third and tallest flyover—Loop 1604 westbound to I-10 eastbound—on August 28, 2025. The tallest ramp measures approximately high and long, once lower construction is finished, requiring extensive structural supports and multi-span bridge engineering. The fourth connector, carrying Loop 1604 eastbound to I-10 eastbound traffic, opened on September 13, 2025. The fifth connector, carrying I-10 westbound to Loop 1604 eastbound traffic, opened on October 4, 2025. The connectors from I-10 eastbound to both directions of Loop 1604 are scheduled to open on November 17, 2025. Construction is expected to conclude by late 2026, with additional connectors, frontage road reconfigurations, and landscaping enhancements scheduled for completion in the final phase. Throughout the process, TxDOT coordinated closely with local businesses, residents, and emergency responders to maintain corridor accessibility.

Date	Milestone	Notes
December 2024	First direct-connect opens	Loop 1604 eastbound to I-10 westbound
June 2025	Second direct-connect opens	I-10 westbound to Loop 1604 westbound
August 2025	Third and tallest flyover opens	Loop 1604 westbound to I-10 eastbound
September 2025	Fourth direct-connect opens	Loop 1604 eastbound to I-10 eastbound
October 2025	Fifth direct connect opens	I-10 westbound to Loop 1604 eastbound

Funding and cost

The Loop 1604/I-10 interchange is one of the largest single infrastructure investments in San Antonio's recent history. According to TxDOT planning documents, the total cost of the interchange reconstruction is estimated at approximately $615 million. Funding comes from a combination of state highway funds, federal transportation grants, and local contributions managed through the Alamo Area Metropolitan Planning Organization. Roughly 60% of the project is financed through TxDOT's Unified Transportation Program, while federal Surface Transportation Block Grants account for approximately 25% of total funding. Local governments and regional mobility authorities contributed the remaining share to support frontage road enhancements and landscaping improvements. Cost estimates increased during construction due to inflation, material shortages, and unexpected structural modifications required for tall flyover supports. TxDOT reported that roughly one-third of the project's budget is allocated to bridge engineering and elevated ramp construction, making it one of the costliest highway flyovers in Texas per linear mile. As part of cost management, phased contracts allowed the agency to control spending while adapting to supply chain challenges during 2023 and 2024.

Engineering challenges

The interchange's unusual height and complexity presented significant engineering challenges. Constructing a five-level stack with flyovers reaching required deep foundation drilling, extensive soil stabilization, and advanced bridge segment casting techniques. TxDOT engineers used geotechnical surveys to design foundation systems capable of withstanding substantial lateral wind forces due to the structure's elevation. To ensure structural performance, high-strength concrete mixes and prestressed girders were deployed on the tallest connectors. The project also had to contend with limited right-of-way and nearby developments, forcing creative staging strategies to maintain traffic access during construction. Environmental constraints included stormwater management, habitat preservation, and mitigation of noise impacts for surrounding residential areas. Weather disruptions, including heavy rainfall events in 2023, caused minor schedule delays during the early phases. Given the interchange's location near multiple retail and educational centers, engineers also had to coordinate construction schedules around major event traffic at Six Flags Fiesta Texas and UTSA. The interchange has been cited as a case study in balancing structural safety, traffic flow, and environmental impacts within a highly urbanized growth corridor.

Traffic and safety

Once completed, the interchange is projected to handle over 350,000 vehicles per day by 2035, according to TxDOT traffic studies. The previous cloverleaf design suffered from significant congestion during peak hours, with backups regularly exceeding on major approaches. Early traffic monitoring data following the December 2024 opening phase indicates reduced travel times and fewer lane-change conflicts on direct connectors. Safety upgrades include wider shoulders, improved sight distances, and redesigned merging zones to reduce collision risks. TxDOT also incorporated intelligent transportation system components, such as dynamic message signs and real-time traffic monitoring, to manage peak flows more efficiently. The frontage road roundabouts are expected to lower crash severity by replacing traditional signalized intersections with lower-speed circular designs. Pedestrian crosswalks and protected cycling paths were included in limited locations to accommodate multimodal travel demands. Long-term projections suggest that the interchange will delay the onset of severe congestion by at least 15 years compared to baseline growth models. Regional planning agencies view the project as critical for maintaining connectivity between San Antonio's central business district, suburban employment centers, and neighboring Hill Country communities.