The Pennsylvania Department of Transportation lowered speed limits on several major highways Thursday morning as winter weather moved through the northwest part of the state.

Officials reduced speeds to 45 mph on all interstates in the region. In Mercer County, the restriction affects Interstate 80 from the Ohio state line to Clarion County. Drivers on Interstate 79 will also see the lower limit starting at the Interstate 80 interchange and continuing north to Erie.

The 45 mph limit also applies to Interstate 376 from the Interstate 80 interchange south to the Poland exit in Lawrence County.

PennDOT representatives asked motorists to stay off the roads if possible. For those who must drive, the agency requires commercial vehicles to stay in the right lane while the restrictions remain in place.

Other affected roads in the region include the entire lengths of Interstate 86 and Interstate 90 between the Ohio and New York borders.