TRAFFIC UPDATES: Roads across the north island have been impacted by recent weather events. We’ll provide updates on our Journey Planner website as information becomes available. View our traffic map for road closures and delays(external link)

SCAM ALERTS: Report a phishing scam or learn about the latest phishing emails

CONTACT CENTRE WAIT TIMES: Our Contact Centre is currently experiencing significant wait times. View frequently asked questions

ONLINE TRANSACTIONS: We are experiencing issues with credit and debit card transactions on our website. We are working with the payment provider to resolve this as soon as we can. 

CONTACT CENTRE WAIT TIMES: Our Contact Centre is currently experiencing significant wait times. View frequently asked questions

REGO AND RUC LABEL ERROR: There was a postage error with labels purchased on the 15 August 2022. Find out more

ROAD USER CHARGES (RUC) DISCOUNT: Find out more about the temporary RUC reduction scheme

ONLINE SERVICES: We are currently experiencing issues with all our online services at the moment. We are working to resolve the services as soon as possible. We apologise for any inconvenience caused.

COVID-19 SERVICES UPDATE: Information on Waka Kotahi services, extensions and more

ONLINE SERVICES: We currently have an issue with receiving some payments and are working to resolve this issue as quickly as possible. We apologise for any inconvenience.

EASTER WEEKEND – PLAN AHEAD: Heading away for the long weekend? Check our holiday journeys tool(external link)

SCAM ALERTS: Refund email and Vehicle licence (rego) renewal phishing emails

CONTACT CENTRE PHONE LINES: Our Contact Centre phone lines are currently unavailable. View frequently asked questions

SH20 Manukau Harbour Crossing

Section menu

Project introduction

Manukau Harbour Crossing doubled the traffic capacity of State Highway 20 between Queenstown Road and Walmsley Road, including duplicating the Mangere Bridge.

  • Estimated project dates

    Feb 2008–Aug 2010
  • Estimated project cost

    $100 million +
  • Project type

    Infrastructure upgrade
  • Project status


Project updates


The Manukau Harbour Crossing project made it safer, quicker and easier to travel on State Highway 20 across Manukau Harbour between Mangere and Onehunga. It has local, regional and national benefits for business, industry and tourism.




  • Improve access to and from south and central Auckland.
  • Increase traffic capacity and provide priority for buses across the Manukau Harbour.
  • Improve travel times to and from the airport.
  • Improve access to local and arterial roads.
  • Provide better links between the Mangere Bridge and Onehunga townships.
  • Provide better pedestrian and cycle links, including access to the Manukau Harbour.
  • Provide future proofing for a rail corridor by shifting the motorway alignment to the east, between the Mangere Bridge and Walmsley Road, and building extra strength into the new bridge’s foundations.

Project features

  • A duplicate motorway bridge over the Manukau Harbour to give four traffic lanes and bus shoulder lanes in each direction.
  • The Southwestern Motorway widened to three traffic lanes and a bus shoulder lane in each direction, extending to Queenstown Road and SH20 Mt Roskill Extension in the north and to Walmsley Road in the south.
  • Replacement pedestrian overbridges at Beachcroft Avenue (Onehunga) and Hastie Avenue (Mangere Bridge).
  • A new pedestrian and cycle overbridge across Onehunga Harbour Road, providing safe traffic-free access between Onehunga Hall and the old Mangere Bridge.
  • A new pedestrian and cycle route under the southern approach of Mangere Bridge from Coronation Road to Mahunga Drive.
  • Protection and enhancement of the natural, social and physical environment around the project area by:
    • managing the project in an environmentally responsible manner
    • protecting and enhancing the local environment
    • implementing systems to reduce construction waste
    • minimising dust and noise
    • extensive landscaping and planting.
  • Enhanced treatment of stormwater from the motorway to improve the quality of water entering the Manukau Harbour.
  • Reinstatement of the Waterfront Road Reserve upon completion of the project.

Our partners on this project