Police responded to Algonquin Road near Meadowbrook Industrial Court about 9:15 a.m. for a report of a car hitting a pedestrian.
When officers arrived, they found a man in the roadway, police said.
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He was taken to a hospital for treatment of life-threatening injuries.
The driver of the vehicle involved is cooperating with police.
Algonquin Road between Barker Avenue and New Wilke Road is closed to both eastbound and westbound traffic during the investigation.
Chopper 7 was over the scene about 11:30 a.m., and a red sedan was near the scene.