Highway 1 is to be closed to all traffic for four nights starting July 9 about 21 miles north of the San Luis Obispo/Monterey county line.

Due to road work at Rain Rocks, the highway will close at 9 p.m. Monday through Thursday nights, reopening at 6 a.m. Tuesday through Friday, Caltrans has announced.

Roof panels are to be placed overhead on a rock shed about 1.8 miles south of Lucia. Electronic message signs will alert motorists at each end of the closure and at three other locations.

Emergency vehicles will be allowed through, although it may involve delays of up to 30 minutes.

Caltrans is projecting that all roadwork on the $30 million roadway rebuilding project should be complete by spring 2013.

For details, call (888) 836-0866 or go to www.dot.ca.gov/dist05/projects. For current traffic conditions on highways statewide, call (800) 427-7623.