Designing the First Undercrossing DDI in California

How a Diverging Diamond Interchange Improved Safety, Mobility and Access at a Critical San Bernardino Gateway

The Interstate 215/University Parkway Interchange in San Bernardino, California, was long one of the most congested intersections in Caltrans District 8. But the construction of a diverging diamond interchange (DDI), completed in May 2026, has transformed it into a safer, more efficient gateway.  

Writing about the interchange in a recent issue of Roads & Bridges magazine, HDR project leaders shared how it improves traffic operations, enhances safety and adds pedestrian and bicycle connectivity — all within a constrained urban footprint and without widening the existing freeway bridge.

The article was written by Mark Hager, senior highway project manager; Julian Hernandez, senior highway engineer and Brian Smith, senior highway project manager. Together, they have more than 75 years of transportation industry experience.  

The Roads & Bridges story highlights the collaborative effort among the San Bernardino County Transportation Authority, Caltrans, the City of San Bernardino and California State University, San Bernardino to deliver the district's first constructed diverging diamond interchange and provides a valuable insight into how transportation teams can rethink aging infrastructure to better serve communities.

“Earlier concepts carried estimated price tags of over $100 million once bridge reconstruction and property impacts were considered,” the authors wrote. “By working within existing constraints, the final project was delivered for a fraction of that amount, with construction bids coming in under $20 million.”

Read the full article, “Designed to Diverge,” in the July/August 2026 issue of Roads & Bridges magazine.