One lane on the northbound and southbound sides of the Highway 101 bridge over the Santa Maria River will be closed during overnight hours starting Tuesday, Caltrans officials said.

The work is part of the bridge’s $31 million widening project. The bridge between Nipomo and Santa Maria will be widened from two to three lanes in each direction and a bike path will be added to the span as well.

The closure will be from 7 p.m. to 6 a.m. Caltrans does not have an ending date for the work.