The OPP has reopened the northbound lanes of Highway 400 approaching Barrie after icy conditions and four separate crashes prompted the closure.

The collisions happened north of Highway 89 around 4 a.m. Friday.

Sgt. Dave Woodford said two involved tractor-trailers.

In one, a woman was taken to hospital with life-threatening injuries after her car flipped on its roof. In the other, a person was taken to hospital with serious, but non-life-threatening injuries.

“It’s actually like a skating rink out there where the salters have not been,” Wood ford said.

“We’re telling drivers to be really careful … it’s cold and the conditions change rapidly, especially on the on-ramps and off-ramps and under the underpasses.”

The stretch of Highway 400 between Highway 89 and Innisfil Beach Road was closed for about five hours.