Drivers headed through Pittsburg and Antioch on Highway 4 in the overnight hours later this week may want to give themselves a few more minutes to account for road detours.

All Highway 4 eastbound lanes will be closed from the Loveridge Road exit in Pittsburg to Somersville Road/Auto Center Drive from midnight to 5 a.m. Friday morning, as crews shift traffic onto a portion of the recently-completed eastbound bridge over Somersville/Auto Center, according to a Caltrans news release.

The shift represents a milestone in the widening of Highway 4 from four to eight lanes through Antioch, local transportation officials said.

Around the same time, all westbound lanes of the freeway will be closed between the Lone Tree Way/A Street and Contra Loma Boulevard/L Street exits -- from 11 p.m. to 3 a.m. Friday morning, as crews remove formwork from the G Street overcrossing.

That same stretch in the eastbound direction will be closed from 2 to 6 a.m. Saturday morning.

For the Loveridge closure, eastbound motorists Friday will be directed off the highway at Loveridge and down Leland Road and Delta Fair Boulevard to Somersville.

Westbound motorists will be detoured down A Street, and west on East 18th Street to L Street and back on the freeway. Eastbound drivers Saturday morning will be directed off at Contra Loma to Fitzuren Road, and up Putnam Street to Lone Tree.

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

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