Press Release – NZTA From next week there will be lane changes for people using the Northern Motorway as 16,000m3 of material, the equivalent of six Olympic sized swimming pools,is excavated to create an underpass providing a direct connection between SH1 and SH18 as part of Auckland’s Northern Corridor Improvements (NCI) project. “The underpass will provide a direct motorway to motorway connection for people travelling from the north heading west. When NCI is complete, it will be the final link of the western ring route”, says Waka Kotahi NZ Transport Agency National Manager Infrastructure Delivery Andrew Thackwray. Construction of the underpass began just over two years ago and is being built using a ‘top-down’ construction method which means that the roof and walls are constructed first and then the material under the roof excavated and taken away.