A Guelph man was taken to hospital Friday night after his vehicle rolled over on Highway 401, just east of the Homer Watson exit.
It happened in the eastbound lanes just before 9 p.m.
The 66-year-old driver was taken to a trauma centre with what police are calling potentially life-threatening injuries.
OPP say he was ejected from the vehicle.
Ornge Air Ambulance was initially called to the scene but it was later cancelled.
Police are still investigating the circumstances leading up to the crash.
"We are looking at speaking to witnesses who have dashcam that can assist us in this investigaiton," said Sgt. Kerry Schmidt.
