San Antonio- One of the largest transportation projects in North San Antonio has entered its final phase, bringing a dramatically different traffic pattern—and the promise of long-term congestion relief—to the busy intersection of Loop 1604 and Blanco Road.
Earlier this year, the Texas Department of Transportation (TxDOT) shifted traffic onto the region’s first-ever diverging diamond interchange (DDI), a design intended to move vehicles through the intersection more efficiently while reducing crashes. The final phase of construction is expected to wrap up in late summer 2026, although motorists should continue to expect overnight lane closures and periodic traffic changes until the project is complete.
For many drivers, the first experience with the new interchange was unexpected. Instead of remaining on the right side of the road, traffic on Blanco Road briefly crosses to the left side while traveling over Loop 1604 before returning to the traditional pattern. Although unusual at first glance, transportation engineers say the design allows left-turning vehicles to move without crossing oncoming traffic, reducing delays and improving safety. A traditional interchange has 26 vehicle conflict points, while a diverging diamond has just 14. National studies cited by TxDOT have shown the design can significantly reduce crashes.
The Blanco Road intersection serves as a gateway to some of San Antonio’s fastest-growing neighborhoods, including Stone Oak, Hollywood Park, Hill Country Village, and nearby commercial districts. Thousands of commuters use the corridor daily to reach employers, schools, shopping centers, and medical facilities.
The interchange project includes new bridges, expanded lanes, frontage road improvements, dedicated bypass lanes beneath Blanco Road, upgraded traffic signals, sidewalks, and bicycle accommodations. Through traffic on the Loop 1604 frontage roads now uses bypass ramps that eliminate the need to stop at the Blanco Road intersection, improving overall traffic flow.
The Blanco Road work is one segment of TxDOT’s $1.4 billion Loop 1604 North Expansion Project, which stretches approximately 23 miles from Bandera Road to Interstate 35. The broader effort will widen Loop 1604, add high-occupancy vehicle lanes, reconstruct major interchanges, and modernize one of the busiest transportation corridors in Texas. TxDOT estimates the completed improvements will significantly reduce future travel times while enhancing safety throughout North Bexar County.
Businesses near the interchange have weathered several years of construction while continuing to serve customers. Although changing traffic patterns have occasionally affected access, many owners believe the finished project will improve visibility and make the area easier to navigate for residents and visitors alike.
For now, drivers are encouraged to slow down through the work zone, follow overhead signs carefully, and allow extra travel time during peak commuting hours. As crews complete concrete islands, install permanent signs, and finish landscaping and pavement work, periodic nighttime closures are expected to continue.
When construction concludes later this summer, the Blanco Road interchange will represent a milestone for San Antonio transportation infrastructure—the city’s first diverging diamond interchange and a key piece of a larger effort to prepare the rapidly growing North Side for decades of future traffic.