One woman is dead and her brother is in hospital following a head-on collision Saturday night on Highway 407.

The Ontario Provincial Police say at about 9 p.m. a Mazda 3 was travelling east in the west-bound lanes of Highway 407 near Highway 403 when it collided head-on with a Toyota Corolla.

The passenger in the Toyota, 47-year-old Carol Grimmond of Windsor, Ontario, was transported to Credit Valley Hospital where she was pronounced dead, according to OPP Sgt. Dave Woodford. Her brother, who was driving, was also sent to hospital with minor injuries.

The woman driving the Mazda suffered no injuries, and was arrested at the scene for alleged impaired driving. Mary Sampson, 55, of Oakville, Ontario faces charges including impaired driving causing death.

Woodford noted that the OPP is out in force this holiday weekend, watching for impaired drivers.

“We don’t take it away from anybody to have a good time and drink — but they’ve got to be responsible and not get behind the wheel of a car,” he said.

The OPP saw a similar case in August when an SUV going the wrong way near the QEW and Highway 427 ran head-on into another vehicle, killing a father and daughter.

Alcohol is often but not always a factor in such cases, said Woodford.

“Sometimes people have a medical condition and they don’t know where they are, they lose their sense of direction,” he said.

With files from CBC's Natalie Kalata