Emergency officials have moved a crashed truck from its precarious position on the edge of the approach to the Bolte Bridge, in Melbourne, after a dramatic early morning accident.

Police believe the large truck was travelling southbound in the right hand lane on CityLink at around 6:30am (AEST) when a car tried to merge in front of it.

It is believed the truck jackknifed while trying to take evasive action and then bounced across the freeway coming to rest on top of one of the side barriers.

The trailers dangled precariously over the side of the bridge and the driver fell from the upside down cabin.

He landed on top of some concrete debris 15 metres below and is in critical condition at the Royal Melbourne Hospital.

The driver of the car that hit the truck has been taken to the Alfred Hospital with minor injuries.

The accident caused rush hour traffic chaos across the city and emergency crews are racing to clear the bridge in time for the evening commute.

One eyewitness described it as being like a crash in a Hollywood movie.

Seven hours after the crash, a crane carefully lifted the truck off the side of the bridge and on to the roadway, as trains on the Upfield line were temporarily halted as a precaution.

The MFB brought in a small drone to take pictures of the side of the truck that they could not see from the bridge and a cherry picker was used to examine the vehicle before it was moved.

CityLink is not sure when southbound lanes will reopen and it is not clear when the truck will be removed.

Peter Eagan from the Metropolitan Fire Brigade is hopeful the freeway will be open in the next few hours.

"I'm hoping it will be open for the evening peak. If not I'll be disappointed."