A 53-year-old Mississauga man has been killed on Highway 401 after he was struck while changing a flat tire.

The accident happened around 4 p.m. on Highway 401 near Dixon Road on one of the highway's off ramps.

The victim was on the driver's side of the car when a Nissan veered to the right and struck the man, propelling him into the grass.

The man was killed instantly.

A distraught woman, the driver of the Nissan, was seen being escorted to an ambulance.

Ontario Provincial Police Constable David Woodford reminded drivers to take extra precautions if they have to pull over.

"We suggest that even if you're involved in a collision that you don't get out and wander around the highway. Call for an emergency vehicle or tow truck and they'll come in behind. They have the emergency lights and they'll activate them," Woodford said at the scene of the accident.

"So, stay in your vehicle until someone comes and then we can assist or then you can change your tire or do whatever you have to do, but it's always safe to wait for an emergency vehicle to arrive on scene."

Three out of five lanes on the westbound 401 were closed after the accident.

Police expect the lanes to be reopened around 7 p.m. but traffic delays are expected for some time.

With a report from CTV's Paul Bliss