Emergency services were called to the scene on Rangiora Woodend Road at 9.30 am at a five-way intersection.
St John said an ambulance and a rapid response vehicle responded and treated one patient.
The trapped female driver had to be extracted by Fire and Emergency and was transported to Christchurch Hospital in a serious condition.
A witness said courier parcels were scattered over the road and had to be cleaned up by New Zealand Post workers.

Emergency services at serious car crash between Rangiora and Woodend. Photo: George Heard