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SH16 Causeway Upgrade Project

The causeway upgrade is a 4.5 kilometre-long project between the Great North Road Interchange and the Te Atatu interchange, and is a key component in completing the Western Ring Route road of national significance project. The existing six-lane causeway will be widened to provide additional lanes in both directions. The shoulder lanes for buses will be widened and extended, and there will be improvements to the pedestrian and cycleway beside the motorway. The causeway will also be raised to prevent flooding during extreme tidal conditions, and stormwater will be treated to a higher standard before it is discharged into the Waitemata Harbour.

The causeway runs besides the Motu Manawa - Pollen Island Marine Reserve. Design data has been gathered during the causeway trial, which took place during 2012, to ensure that the Causeway Upgrade will have as little impact on the Marine Reserve as possible.

All projects

The causeway along SH16 will be raised and widened to increase capacity and reduce flooding..

The causeway along SH16 will be raised and widened to increase capacity and reduce flooding.


  • Other names

    SH16 Causeway
  • Part of

    Western Ring Route, a Road of National Significance
  • Estimated start date

    May 2013
  • Construction start date

    May 2013
  • Estimated completion date

  • Location

    SH16 between Great North Road Interchange and Te Atatu interchange
  • Project type

    Corridor Improvements
  • Project status

  • Project contact

    Elizabeth Collins
  • Estimated cost

    $100 million +
  • Project website

Project purpose

To upgrade an important part of the Western Ring Route road of national significance project.


The Causeway is a key part of the Western Ring Route - one of the Government's seven roads of national significance to help promote economic growth. Once completed, the Western Ring Route will provide a strategic alternative to SH1, central Auckland and the Auckland Harbour Bridge. It will link with the Waterview Connection project and its new interchange at Great North Road - connecting SH16 with the Southwestern Motorway (SH20).

The causeway upgrade will provide the following benefits to road users:

  • Improved traffic flow and travel times with the addition of more lanes
  • Less flooding on the causeway
  • Quicker bus trips
  • Improved pedestrian and cyclist access across the motorway.


As part of the Causeway Upgrade Project, NZTA and its alliance partners will:

  • Widen the causeway to add lanes and create more capacity
  • Raise the causeway and the adjacent cycleway to reduce flooding
  • Construct new bus priority lanes on the motorway shoulders
  • Improve access across the motorway for pedestrians and cyclists

The Causeway Alliance

The Transport Agency has engaged the Causeway Alliance to deliver the Causeway Upgrade Project from Great North Road west to the Whau River bridge just before Te Atatu, a 4.8km stretch of State Highway 16.

The Causeway Alliance is made up of AECOM, Coffey, Fulton Hogan, Leighton Contractors, Sinclair Knight Merz and Transport Agency itself, bringing together specialist skills in a range of safety, engineering, design, construction, environmental protection, management, community engagement, commercial and support disciplines.