ANTIOCH -- Motorists headed westbound toward Pittsburg on Highway 4 overnight Thursday and Friday will have to find an alternate route.

All westbound lanes of Highway 4 will be closed between the Lone Tree Way/A Street and Somersville Road/Auto Center Drive exits from midnight to 3 a.m. both nights as overhead signs are installed across those lanes, according to a Caltrans news release.

Drivers will be detoured off Highway 4 at A Street and west on East 18th St and Sycamore Drive to Auto Center and eventually back onto the freeway.

Upon completion in 2015, the roadwork will widen Highway 4 from four to eight lanes from Loveridge Road in Pittsburg through Antioch to the intersection with Highway 160.

For roadwork information, visit http://4eastcounty.org.

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