Up to the 1950s, much of the freight traffic in Canterbury involved services between rural areas and the major centres and ports. Manufactured imports were distributed mainly from Christchurch and Dunedin, with agricultural produce exported from Port Chalmers, Oamaru, Timaru and Lyttelton. The South Island Main Trunk connected the major centres to the branch lines rather than handling long-haul traffic. Since the 1950s, with the decline in the branch line network, the role of the South Island Main Trunk has changed with it now handling predominantly long-haul freight, a change brought about in part by the containerisation of freight handling and the inter-island ferries.