The man and woman from Canberra were out of the car changing a tyre on the side of the road when the truck veered off the road and hit the trailer.

The truck continued up the road and tipped over onto the driver's side door.

The truck driver from Melbourne was trapped for three hours while a team worked to free him from the wreck. Once cut free the Snowy Hydro Southcare helicopter flew him to Canberra Hospital where he underwent surgery.

The man from the car had a broken leg and was awaiting surgery. The woman was taken to Yass District Hospital with chest and ankle injuries.

Northbound lanes of the Hume Highway were closed for several hours and traffic was being diverted.

Detectives from Cootamundra and Albury crime scene inspectors attended. One lane was still closed  until around 12.30pm today.

The incident has prompted police to remind motorists of the need to exercise extra caution on the roads over the coming weeks.

NSW Police said motorists need to drive to the conditions at all times.

“Any motorist pulling into a breakdown lane or road shoulder needs to do so at a safe speed and ensure they park their vehicle in a visible location that is as far away from passing traffic as possible,” operations commander, Superintendent Smith said.

“Whether you are driving on a freeway, highway or suburban street, please stick to the road rules, drive to the conditions and exercise caution at all times.

“It only takes a split second lapse in concentration for a serious crash to occur.”