"They’re coming together at 200 km/h, in the dark out of nowhere," Ontario Provincial Police Const. Brad Muir said.
"It’s pretty rare when it happens, but it seems when it does, someone is pretty seriously injured or killed," he said.
The 41-year-old woman had just left her Oakville home around 9 p.m. Sept. 14 on her way to watch her eldest daughter, 15, perform at an event.
She was less than 10 km from her house on Queen Elizabeth Way when the tandem wheels broke free from an east-bound tractor-trailer and bounced over the median onto her car.
The wheels kept bouncing, striking the top of another tractor-trailer’s cab.
Police said the trucker who lost the wheels was unaware of what happened until officers pulled him over near Sherway Gardens.
Muir said he was co-operating with investigators and gave a statement Thursday night.
Officers had to get a search warrant before they could begin inspecting the truck, now parked at an Etobicoke industrial yard.
Muir said early indications are the wheels’ bearings failed.
He said maintenance records and the driver’s pre-trip inspection will also be closely looked at.