Northern Corridor Improvements project completes Western Ring Route


Aucklanders are one step closer to a more resilient state highway network as the direct link from State Highway 1 (SH1) to State Highway 18 (SH18) is set to open early next week.

One of the final stages of the Northern Corridor Improvements project, the two-kilometre link between SH1 and SH18, including an underpass also officially completes the Western Ring Route, providing a seamless and robust alternative to SH1.

“Reliable journey times for people and freight will be a bi-product of the work that has taken place across multiple years and projects to improve the resilience and performance of Auckland’s transport network, protecting our infrastructure against the elements and providing a choice for people who need to get around Auckland” says Stephen Collett, Regional Manager Transport Services Waka Kotahi.

“The direct motorway link from SH18 to SH1 which was opened last month has already established a seamless transition for motorists travelling from the west to the north and the opening of this underpass will do the same in the other direction.”

Sitting halfway within the link below SH1, the underpass was built in five stages around live traffic. This required work to be completed in sections so that crews could shift traffic as they moved through each phase of works.

In total, approximately 16,000m³ of material (the equivalent of six Olympic sized swimming pools) was excavated to create the ‘hole’ of the underpass. Work began on excavating the underpass in mid-2021.

Eight metre-high concrete panels which weigh approximately 13 tonnes each line the walls of the underpass. The colours which feature inside the underpass reflect the changing colour of the surrounding landscape from the coastline to the east and the Waitakere Ranges to the west.

“The urban design narrative was developed in partnership with mana whenua to reflect the cultural history of the area. The elements which feature on the entrance to the underpass reflect the Pātiki design which is based on the diamond shape of the flounder fish to represent the diverse kai caught and transported through the area” says Mr Collett.

The shared path which runs parallel to SH1 from Constellation Station to Oteha Valley Road will open shortly, giving locals a greater choice in how they travel around their community.

For more information on the project, please visit: