MANTECA, Calif. — History will literally be set in stone in Manteca when California's first Diverging Diamond Interchange (DDI) is finished in the city.

While other states like Nevada have already installed four of these unique designs, California's first DDI isn't far from becoming a reality.

"We are expecting to complete the project by late this year or early 2021 but the schedule depends on the weather," said Koosun Kim, Acting Public Works director for Manteca.

The project was delayed by for four months after PG&E started its utility replacement process in December 2019, but PG&E's work is expected wrap up in February, Kim said.

In the meantime, contractors worked on the two new ramps and structures for the bike and pedestrian paths on the east side of the project.


The innovative design might look intimidating, but it actually makes traffic safer by reducing the potential accident locations from 26 to 14, according to Matt Brogan, a principal-vice president at Mark Thomas, the Sacramento-based company designing the DDI.

A DDI has drivers enter from the right side of the road, cross to the left side as they go through the interchange, and cross back again to the right.

This crisscross pattern keeps traffic moving through the intersections and provides free left-turn movements for drivers heading on and off the freeway.

071119 diverging diamond manteca full
The diverging diamond intersection reduces potential accident locations from 26 to 14.
Courtesy: Mark Thomas

It might seem confusing, but the concept is simple. If you want to make a left-hand turn at the interchange, stick to the left lane and you'll get a free left turn movement onto the freeway. If you want to make a right-hand turn, stick to the right lane and you'll get a free right turn movement. 

With the design, it'll cause traffic to move slower but more efficiently. More cars will be able to go through at a slower speed as opposed to going at higher speeds and waiting at a light, according Devin Cartwright, who developed Nevada's first DDI with their Department of Transportation.

Daniel Padilla, city engineer for Ceres, confirmed Ceres will also be getting a DDI in the future, but they don't expect to see construction for about two to three years.

01082020 diverging diamond manteca
A new exhibit for the Diverging Diamond Interchange project in Manteca provided by acting public works director Koosun Kim.
City of Manteca/Mark Thomas


Download on the App StoreGet it on Google Play

Stay In the Know! Sign up now for ABC10's Daily Blend Newsletter

WATCH ALSO: Connect the Dots: Manteca's Great Wolf Lodge water park comes with a catch