2009, the Northern Motorway was extended to Puhoi, bypassing Hibiscus Coast Highway through Orewa which was re-designated part of SH 17. However, SH 17 was short lived, being revoked in September 2012 and reverting to a local arterial road. The Auckland Southern Motorway was built between 1953 and 1978, bypassing the former route via Great South Road. The construction of the Central Motorway Junction between 1973 and 1978 connected the Northern and Southern Motorways, taking State Highway 1 off inner Auckland streets. The Waikato Expressway north of Te Kauwhata has largely been built on the existing line of SH 1N, although at Pōkeno the highway was diverted to bypass the town to the east. South of Te Kauwhata, most of the expressway has been built on a new line bypassing the towns of Ohinewai, Ngāruawāhia, Te Rapa and Cambridge, as well as the city of Hamilton. Most old sections of SH 1N reverted to local arterial roads, while the former section through Hamilton became the SH 1C spur. Construction of the Peka Peka to Ōtaki extension to the Kapiti Expressway began in mid 2017 and opened to traffic in December 2022. The project added of expressway to the northern end of the Kapiti Expressway at Peka Peka, to terminate north of Ōtaki at Taylors Road. The controversial Transmission Gully Motorway began construction in 2014, and was officially opened on 30 March 2022. It provides a new alignment for State Highway 1 between Mackays Crossing and Linden, diverting the route from the Centennial Highway between Paekakariki and Pukerua Bay, as well as providing an eastern bypass of Porirua. The previous route of State Highway 1 was renumbered to State Highway 59 on 7 December 2021, which created a temporary gap in the SH 1 designation until the new motorway opened. The Johnsonville-Porirua Motorway was constructed in the 1940s and 1950s to replace the Old Porirua Road. The first section of motorway between Johnsonville and Takapu Road opened on 23 December 1950, and is New Zealand's oldest motorway. The Wellington Urban Motorway was constructed between 1969 and 1978, but was originally part of State Highway 2 as it could only be accessed from the Hutt Valley. The construction of the Ngauranga Interchange flyovers in 1984 allowed SH 1 to be diverted onto the motorway, bypassing central Wellington streets. The Christchurch Northern Motorway opened in October 1967 between Tram Road and Belfast, providing