The eastbound collector lanes from Highway 410 to Dixie Road were closed while police investigated the circumstances surrounding the accident.
The southbound ramp from Highway 410 to the eastbound collectors and the eastbound ramp from Highway 403 to the eastbound Highway 401 collectors were also closed.
OPP say a tractor-trailer was rear-ended by a car at about 3 a.m.
The driver of the car died in the accident. The driver of the tractor-trailer was not injured.
Police reopened the highway just after 7 a.m. — in time for the early morning rush hour.