By allowing ads to appear on this site, you support the local businesses who, in turn, support great journalism.
Union/120 Bypass diverging diamond meeting set
interchange copy
A rendering of the diverging diamond interchange planned for the 120 Bypass and Union Road.

Union Road 23 years ago didn’t even have on– and off-ramps to the 120 Bypass.
South of the freeway was nothing but small rural estates and farmland.
Later this year, Manteca will be breaking ground on California’s first diverging diamond interchange to serve the rapidly  growing South Manteca area that within 20 years could be home to more than 60 percent of the city’s population and numerous retail endeavors.
An updated information meeting for the project is taking place Tuesday, April 10, from 5 to 7 p.m. at the Manteca Senior Center, 295 Cherry Lane. City and Caltrans District 10 representatives will provide an update on the design and construction schedule. Physical work is expected to start this fall.
The diverging diamond design has been used successfully elsewhere in the country to significantly improve traffic flows by reducing the need for traffic signals, enhancing safety and reducing construction cists, The nearest diverging diamond is in Reno on Interstate 580 at Mona Lane.
The diverging diamond design calls for traffic lanes crossing  on either side of the bridge structure so northbound traffic would cross the bridge on the west side instead of the east side with the southbound lanes on the east side instead of the west side. Once they clear the bridge they are switched back.
The on and off ramps along with the flipping of the lanes creates two semi-diamond shaped intersections on either side of the bridge. This eliminates the need for traffic from both directions on Union Road as well as that coming from the 120 Bypass to avoid needing any  traffic signals to exit an off ramp or to get into an on ramp. The project will also include ramp meter signals such as now are in place on the Lathrop Road/Highway interchange.
Advantages of a diverging diamond interchange according to Advanced Transportation Solutions/American are:
Fewer conflict points (14 for diverging diamond design, 26 for conventional design).
Better sight distance at turns.
Traffic calming features when desired.
Additional right of way is rarely needed.
Virtually no driver confusion based on a study and observation of existing diverging diamond design interchanges.
Construction time is reduced.
Wrong way entry to ramps extremely difficult.
Pedestrian crossings are shorter.
Maintenance of traffic is simplified during construction.
The project will also include a separate pedestrian/bicycle bridge crossing of the 120 Bypass.
When completed Union Road will be four lanes from Atherton Drive to the northern city limits at the northern edge of Del Webb at Woodbridge.

To contact Dennis Wyatt, email