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.