Provincial police say a 54-year-old woman was killed when her car went off the westbound lane of the 401 near Highway 6 north.

There were three other people in the car who were treated for minor injuries but are expected to be alright.

It happened around 3:30 p.m. this afternoon, bringing hundreds of vehicles to a halt.

“Conditions are ideal, and still a collision like this can take place. I would caution everyone to always be aware of your surroundings (and) drive according to your road conditions,” says OPP Constable Graham Williamson.

Police are now re-routing some of the backed-up traffic in one westbound lane. The eastbound lanes are also moving slowly.

Police expect the highway to reopen around 7 p.m.

There is no word on the victim's identity.