The next two interchange upgrades on the 120 Bypass will have six lanes of traffic crossing the new overpasses.

The Manteca City Council on Tuesday approved a cooperative agreement with Caltrans for the diverging diamond interchange (DDI) projects on the 120 Bypass at both Airport Way and Main Street.

The DDI interchanges will be similar to the one at place in Union Road. But instead of replacing two lane overpasses with four lanes as was done at Union Road, the new overpasses will be six lanes.

Plans call for a grade separated bicycle and pedestrian crossings similar to the one in place at Union Road.

Manteca could end up with the most DDI interchanges in California when all three are built. They will also be a mile apart.

Tracy is now building a DDI at International Business Parkway and Interstate 580. Lathrop is planning one at Louise Avenue and Interstate 5.

Other DDI projects planned in California are in Ceres at Hatch Road and Highway 99 as well as Vallejo, San Bernadino, and San Diego.

There were more than 200 DDI interchanges in the United States as of May.

The first DDI in California was the one built at Union Road.

Safety experts —  as well as their counterparts that address traffic flow and congestion issues — like diverging diamonds.

The reasons they give includes being easy to navigate, eliminating last-minute lane changes, and providing better sight distance at turns. All of that results in fewer crashes.

But it has another advantage Manteca leaders appreciate just as much.

They can be built with significantly less money.

That is especially true along the 120 Bypass where a traditional cloverleaf interchange would require taking out existing homes and businesses  to the north of the freeway and then acquiring land to the south.

And given the existing overpass structure can be used as part of the diverging diamond, demolition costs are kept at a minimum.

It also means a shorter time frame for construction that also saves money.

A comprehensive environmental study of the impacts of the two proposed 120 Bypass interchange upgrades is being funded with a $500,000 grant from Measure K sales tax overseen by the San Joaquin Council of Governments.

The work being conducted includes:

*development of detailed engineering plans and specifications.

*detailed project cost estimates.

*recommendation of a preferred alternative.

*approval of final environmental documents.

*approval of monitoring and mitigation measure.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com