Drivers on Highway 4 just east of the Contra Costa County can expect about 40 minutes of extra travel time during the overnight hours next week.

The two-lane rural freeway will be completely closed for work on the Old River bridge from 8 p.m. to 5 a.m. Monday through Friday, ending Saturday morning, for a near three-mile stretch between the bridge and Tracy Boulevard, according to a Caltrans news release.

There will be message signs and a signed detour in place, along with an advisory radio station, to warn drivers, Caltrans said.

Westbound traffic will be detoured south on Tracy Boulevard to westbound Interstate 205 in Tracy and off at Grant Line Road to Byron Highway. Eastbound drivers will be detoured on the same roads, but in the opposite direction.

Highway 4 near Discovery Bay
Highway 4 near Discovery Bay (Karl Mondon, Bay Area News Group)

Farther east, Caltrans will perform intermittent one-way traffic control from 9 a.m. to 2 p.m. all weeks on Highway 4 from Bacon Island Road/ Trapper Road to Roberts Island Road for pavement repair.

Motorists should expect 15-minute delays.

In both instances, Caltrans officials urge drivers to take alternate routes when possible.

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