 NSS had lost most of its trade to road and rail, so switched to inter-island trade, which it gradually lost to Cook Strait ferries from the 1960s, when it increasingly turned to coal and grain, including some trade with Australia, before losing out to natural gas conversions, a shipwreck ("Maranui"), trade fluctuations and reliance on the grain trade, which faltered due to a poor harvest in 1974.NSS briefly tried replacing a ship with a partly owned trucking company, when it closed its Paeroa service in 1947.After the war NSS switched from serving the northern ports to linking some of them to South Island.