ANTIOCH -- Caltrans officials say that a "milestone" has been reached in the project to widen Highway 4 through this city, as half of the G Street overcrossing nears completion.

Traffic on G will be switched on to the new portion of the bridge on the weekend of Nov. 30, according to a Caltrans news release.

All northbound and southbound G Street traffic will be shifted onto the new portion of the G Street bridge, which will allow construction of the eastern half of the bridge, Caltrans said.

Drake Street, Tregallas Road and Minta Lane will be closed during the bridge's construction.

The entire G Street overcrossing is tentatively scheduled to be completed June 2013.

Motorists are advised to expect delays and allow extra commute time.

For information on all Highway 4 closures, visit http://widensr4.org.

Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.