The Central Motorway Junction or CMJ (best known as Spaghetti Junction and rarely as Central Motorway Intersection), is the intersection of State Highways 1 and 16, just south of the central business district of Auckland. A multilevel structure (three traffic levels crossing in several locations), it has been described as a "fiendishly complicated, multi-layered puzzle of concrete, steel and asphalt". Carrying around 200,000 vehicles a day, it is one of the busiest stretches of road in New Zealand.
The central motorway junction forms the intersection between three major motorways: the Northern Motorway (SH1), the Southern Motorway (SH1), and the Northwestern Motorway (SH16), and has several off-ramps for access to the city centre. It is mainly in gullies and cuttings around the CBD, and its construction 1960-1970s removed whole neighbourhoods.
It has somewhat of a hybrid function, falling between a typical ‘X’ interchange and ring road around the city centre. All linkages are direct and there is no separate ring road. The interchange and associated structures encircle the Auckland CBD on three sides, the Auckland waterfront to the north forming the fourth 'border' of central Auckland.
Designed in the 1960s and with most of its links built in the 1970s, the CMJ was a major project in a scheme that led to the forcible acquisition and demolition of 15,000 dwellings in the inner suburbs, causing 50,000 people to move away from the area, with major negative effects on the nearby Auckland CBD, and especially the Karangahape Road shopping area, which fell into decline for decades. Two Catholic schools, St Benedict's College (secondary) and St Benedict's School (primary), were forced to close down.
The CMJ was substantially extended (or in a sense, finally completed) in the 2000s, with the final links opened to traffic in December 2006. During the duration of this NZ$208m project, the existing motorways had to be closed several hundred times during overnight, with traffic rerouted over local roads.