A woman was injured when a 44-tonne truck-and-trailer unit collided with a cow in North Canterbury at about 6.40am this morning.
A second truck then struck the first one, trapping the four occupants inside.
Police said three people were uninjured but a woman was flown to Christchurch Hospital with leg injuries.
The cow had to be put down.
State Highway One near Glen Colwyn has now been reopened.
