Fire department officials in Longueuil, Que., said a portion of the walkway collapsed on to Highway 132, not far from the exit for Roland-Therrien Boulevard.
The walkway appears to have come down about 8 p.m. after being struck by a dump truck used for snow removal, said fire department spokesman Normand Lavallee.
"We believe it has nothing to do with the state of the structure," said Lavallee. "It was an accident."
An ambulance service spokesman said two people were transported to hospital — a woman trapped in a car who sustained minor injuries and a truck driver who was suffering from shock.
The walkway is one of four such structures that link Longueuil to a marina and waterfront on the other side of the highway.
The Transport Quebec website showed the busy highway had been re-opened to traffic early Wednesday.