The Interstate 80 off-ramp onto westbound Jamieson Canyon Road will be closed every night next week for construction, Caltrans said.

The closures will start Monday and last through Saturday night, Caltrans said. On week nights, the off-ramp will be shut from 9 p.m. to 5 a.m. Saturday’s closure will be from 10 p.m. to 5 a.m.

A contractor will install a temporary concrete barrier in preparation for the construction of a $7 million truck climbing lane.

Traffic will be detoured to I-80’s Highway 37 exit in Vallejo, then back to Napa on Highway 29, Caltrans said. Eastbound traffic on Jamieson Canyon will not be affected.

Caltrans is building a 1.2-mile truck climbing lane from the interstate to the top of the grade west of Red Top Road. Construction will take a year.

The new lane should help to prevent rush hour traffic from backing up onto the interstate, Caltrans said.

Plans are under way to double Jamieson Canyon/Highway 12 from two to four lanes from I-80 to Highway 29. This project, estimated to cost $139 million, is several years away from starting construction./Register