A man is in very poor shape after flying off the side of an overpass and crashing onto the highway below.

The driver was heading from Hymus Blvd. to Henri Bourassa Blvd. on the bridge that spans Highway 40 when he went over the retaining wall on the side of the road.

"According to witnesses it's a vehicle that was heading north on the viaduct Henri Bourassa, and for an unknown reason the driver lost control of the vehicle and went to hit the low wall. From there he fell on the service road of the 40 East," said Const. Jean-Pierre Brabant of the Montreal police force.

The car landed on its roof, crushing the vehicle and trapping the driver inside.

Those witnesses called 9-1-1 and emergency crews rushed to the scene.

"They were able after a couple of minutes to take the driver out of the vehicle," said Brabant. "That man, age in his thirties, was transported to a hospital nearby where he was conscious at the moment of his transport but is in critical condition."

"Investigators are working under the hypothesis that the man was speeding and possibly inebriated."

The eastbound service road at Henri Bourassa was closed as soon as crews arrived, and will remain closed during Tuesday's rush hour while police investigators examine the scene and reconstruct the crash.