It happened after 4 a.m. on the southbound lanes of highway 404 north of Elgin Mills Road.
The crash left the pickup truck flipped over.
Early reports suggested that the suspect, a taxi driver under the influence was on the wrong side of the highway but police now say both vehicles were travelling in the same direction.
A woman suffered very serious injuries and was flown to hospital.
Reports by CFRB's Amber Gero
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