Why Loop 1604 at Blanco Road traffic will shift left under TxDOT’s new interchange design

A new traffic pattern is coming to a key North Side junction

Drivers at Loop 1604 and Blanco Road will soon encounter an unfamiliar instruction: stay left. The change is tied to the staged opening of a diverging diamond interchange, a configuration that temporarily moves Blanco Road traffic to the left side of the roadway as it passes over or under the freeway.

The shift is scheduled for March 2026, when construction crews move the intersection into “DDI conditions” as the project enters its final phase. During this traffic switch, the Loop 1604 intersection at Blanco Road is slated for closure overnight from 9 p.m. Friday, March 6, through 5 a.m. Monday, March 9, to allow crews to reconfigure lanes and install traffic control devices.

What a diverging diamond interchange changes—and why traffic crosses to the left

In a diverging diamond interchange, traffic traveling along Blanco Road crosses to the opposite side of the street for a short distance through the interchange, then crosses back. This geometry allows vehicles turning left onto freeway entrance ramps to do so without crossing oncoming traffic, reducing the number of points where vehicle paths conflict.

The design also typically relies on shorter signal phases than a conventional interchange because left-turn movements can be handled more directly. Transportation agencies have promoted the layout for its potential to improve intersection efficiency and safety by simplifying where the most complex movements occur.

What drivers should expect during the final construction phase

Along with the left-side shift on Blanco Road, the final construction phase is expected to bring several operational changes:

• Frontage-road through traffic at Loop 1604 may be directed to use bypass ramps instead of passing straight through the Blanco Road intersection.

• Temporary traffic signals are expected to be in operation as lane patterns change.

• Concrete barriers are planned to separate traffic and provide workspace for building permanent concrete islands.

• Pedestrian access may be limited during parts of the work, and weeknight closures are expected to continue as construction wraps up.

Project timeline and what “complete” means

The March 2026 traffic shift is presented as a transitional step rather than the end of the work. Major roadway and bridge work is scheduled for completion in spring 2026, with additional construction continuing into summer 2026. The diverging diamond interchange itself is scheduled to be complete by late summer 2026.

For drivers, the biggest immediate takeaway is procedural: when crossing Loop 1604 on Blanco Road, traffic will be routed left temporarily as part of the new interchange layout.

With multiple closures and shifting lane configurations possible during the final phase, motorists should anticipate changing work-zone conditions, slower speeds, and additional travel time around the Loop 1604–Blanco Road corridor through at least late summer 2026.