Drivers in north San Antonio will soon see traffic patterns change at Loop 1604 and Blanco Road as TxDOT rolls out a new diverging diamond interchange.
SAN ANTONIO — Drivers in north San Antonio will soon notice something unusual at one of the area’s busiest intersections: traffic briefly shifting to the left side of the road.
The change is part of the Loop 1604 North Expansion Project, where the Texas Department of Transportation is introducing a diverging diamond interchange, often called a DDI, at Loop 1604 and Blanco Road.
While the design may look confusing at first, transportation officials say it’s actually meant to make driving through the intersection faster, smoother and safer.
What exactly is a diverging diamond interchange?
A diverging diamond interchange is a road design where traffic temporarily crosses to the opposite side of the road while passing through the intersection.
At the Blanco Road overpass, drivers traveling through the interchange will shift to the left side of the roadway. This design allows drivers turning left onto the Loop 1604 ramps to do so without crossing oncoming traffic, which helps reduce delays and potential crash points.
Once drivers pass through the interchange, traffic returns to the normal right side of the road.
Transportation officials say the design helps traffic move more efficiently through busy intersections like this one.
Why it’s being built here
The intersection of Loop 1604 and Blanco Road is one of the most heavily traveled areas in north San Antonio.
TxDOT says the diverging diamond design will help reduce congestion and improve safety by allowing traffic to move through the intersection with fewer stops and fewer conflict points between vehicles.
In simple terms, that means shorter waits at red lights and fewer chances for crashes.
When drivers will see the changes
The first big shift happens in March 2026, when drivers will begin traveling through the intersection under DDI traffic conditions.
Construction crews are then expected to complete major roadway and bridge work during spring 2026, with final construction phases continuing into the summer.
TxDOT expects the entire diverging diamond interchange to be complete by late summer 2026.
What drivers should expect during construction
As crews move into the final phase of work, traffic patterns around the intersection will temporarily change.
Drivers traveling along Blanco Road will shift to the left side of the roadway while crossing Loop 1604. Traffic on the Loop 1604 frontage roads will need to use bypass ramps, and temporary traffic signals will help control traffic through the construction zone.
Crews will also install barriers while building concrete islands, and some pedestrian access may be limited during this time. Drivers should also expect weeknight lane closures as construction continues.
Tips for navigating the area
Transportation officials recommend slowing down when traveling through the work zone, paying attention to signs and message boards, and allowing extra travel time.
Workers and heavy equipment will remain active in the area throughout construction, and drivers are asked to follow reduced speed limits and stay alert for shifting traffic patterns.
A different look — but a familiar drive
Even though the design may look different, TxDOT says diverging diamond interchanges are becoming more common across the country because they improve traffic flow and reduce crashes.
Officials say once drivers go through the intersection a few times, navigating the new design should feel just like driving through any other major interchange.