Interstate 90/39 will narrow to one lane during nighttime hours all week in northern Rock County, the state Department of Transportation announced.

Motorists are asked to be alert for crews and equipment near the travel lanes and to watch for slowdowns.

In Janesville, westbound Highway 14/Humes Road under I-90/39 will be closed entirely from 7 p.m. Tuesday to 7 a.m. Wednesday.

Also Tuesday night, one lane of eastbound Highway 14 will be closed in Janesville.

Motorists should find alternate routes, according to a DOT news release.

The lane closures on I-90/39 will be between Milton-Harmony Townline Road and the Rock River bridges near Newville:

• Northbound: 6 p.m. to 5 a.m. Monday through Thursday.

• Southbound: 7 p.m.-5 a.m. Monday through Thursday.

• Both directions: 8 p.m. Friday to 5 a.m. Saturday.

The closures will allow workers to apply lane markings in anticipation of opening the new pavement to three lanes, DOT spokesman Steven Theisen said.

If weather permits, that segment of the Interstate will be open with three lanes in each direction on Saturday, Theisen said.