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New SH20 Mt Roskill Extension motorway opens

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The NZ Transport Agency today opened the SH20 Mt Roskill Extension motorway, the latest link in Auckland's Western Ring Route.

The NZ Transport Agency today opened the SH20 Mt Roskill Extension motorway, the latest link in Auckland’s Western Ring Route.

The 4.5 kilometre extension cost $201m and took four years to build.

The road was officially opened by the Minister of Transport Steven Joyce, during a ribbon cutting ceremony that also included the Mayor of Auckland City, John Banks, NZTA Chief Executive Geoff Dangerfield and Bill Perry, Chief Executive of Fulton Hogan.

The four-lane extension will improve transport connections between south and west Auckland and in the future, between the airport and the central city.  It will also reduce congestion on local roads.    

“This motorway is a response from the NZ Transport Agency to the local community, who wanted some relief from through traffic filtering through their neighbourhoods,” says Wayne McDonald, the NZTA’s Auckland/Northland Regional Director. 

The Mt Roskill Extension includes two interchanges at Hillsborough and Dominion Roads and four bridges to carry local traffic across the motorway at May, Dominion, Hayr and Hillsborough Roads. Two pedestrian/cyclist bridges at Keith Hay Park and Ernie Pinches Street provide safe access to five schools for more than 2,500 students who live in the area.  

“We would like to thank the community for their support over the past four years. It has been a big contribution to a very successful project,” says Mr McDonald.

The motorway has provision for two bus shoulder lanes and rail in the future. A dedicated cycleway developed in conjunction with Auckland City Council alongside the motorway was also opened today. It is part of the Waikaraka cycleway and links to routes in Hillsborough and Mt Roskill.

Auckland City Mayor John Banks says the new motorway extension is a critical part of completing Auckland’s transport network, “This is a twenty-first century motorway which includes world class design that takes into account the special character of this area. Auckland City Council is pleased to have been involved in this significant project from the outset and I’m glad we can complement this piece of motorway with an equally high quality cycleway,” he says. 

Distinctive patterns feature on the motorway’s retaining walls. They symbolise the linking of the Waitemata and Manukau Harbours through the motorway.  Pre-cast concrete panels were imprinted with six different patterns making up a series of “waves.”  

A ‘shotcrete’ method was used at Dominion Road Bridge to create an artificial exposed surface showing the dark red colour and form of the original basalt rock found during construction. The surface was sprayed with concrete and then shaped by hand using templates from the existing rock surface, to create a natural looking face. This surface provides a visual reference to the natural volcanic characteristics of Mt Roskill, which is located directly behind the bridge.

The motorway itself was designed to minimise the amount of excavation needed at the base of Mt Roskill, and the westbound lanes were raised to lessen the impact on the mountain.

The Mt Roskill Extension is part of the central section of the Western Ring Route.  When completed, the route will link the Southwestern (SH20), Northwestern (SH16) and Upper Harbour Motorways (SH18) between Manukau and Albany – a 48 kilometre alternative to State Highway 1 through central Auckland.

Motorway opening information
The opening sequence of the new SH20 Mt Roskill Extension is as follows:

  • The new SH20 Mt Roskill Extension will be opened in the eastbound direction (towards the airport) from the new Sandringham Road roundabout to Queenstown Road Bridge from 3pm Friday 15 May. The link between the new Sandringham Road roundabout and Richardson Road will also be opened in both directions from 3.30pm.
  • The new SH20 Mt Roskill Extension in the westbound direction (towards the city) between Queenstown Road and Hillsborough Road will be closed from 10am Saturday 16 May until 4am Monday 18 May (a signposted detour will be in place via Queenstown Road and Herd Road).
  • The new SH20 Mt Roskill Extension is scheduled to open in the westbound direction from Queenstown Road Bridge to the new Sandringham Road roundabout from 6am Monday 18 May.
  • A 50 km/h speed limit will be in place on the approach to the Sandringham Road roundabout at the western end of the motorway to give motorists time to adjust.
  • Delays are possible as motorists adjust to the new route, so please drive with caution.

In the event of wet weather the westbound direction will be opened on the next fine night during the week of Monday 18 May.

For more information visit www.nzta.govt.nz/mountroskill(external link) or call 09 368 2000.

Background: SH20 Mt Roskill Extension

  • Construction began in September 2005 and was completed on time in May by Fulton Hogan, Opus International Consultants and URS
  • Four lane motorway from Queenstown Road in the south to Maioro Street in the north
  • Two full diamond interchanges at Hillsborough Road and Dominion Road
  • Four bridges for local traffic at Dominion Road, Hillsborough Road, Hayr Road, May Road
  • Two unique cable stay design pedestrian/cyclist bridges at Keith Hay Park and Ernie Pinches Street
  • Hillsborough Road Interchange:
    • Features six lane overbridge, two on-ramps and two off-ramps
    • Up to 40,000 motorists will use the interchange daily and can access the motorway in both directions
    • Temporary signalised roundabout was installed in 2007 for 2 years so that the overbridge could be built, the motorway lowered in the centre and ramps constructed
  • Dominion Road Interchange:
    • Features four lane overbridge, two on-ramps and two off-ramps
    • Helps to ease congestion on Dominion Road, one of Auckland's busiest routes, by providing a local crossing over the motorway

Environmental features:

  • 260,000 new shrubs and 3,400 trees, mostly natives have been planted to restore the local environment
  • Landscaping in the area enhances the basalt features of the volcanic cone
  • Extensive earthworks limited to summer months to limit erosion and sediment
  • During construction, 1.7km of noise walls were put in place to minimise noise
  • Permanent wooden noise walls in place along Maioro Street
  • Four permanent stormwater ponds are in place at Roma Road, Rosemount Road, Keith Hay Park and Melrose Place to filter run-off from the motorway
  • Local aquatic life such as eels from local creeks were relocated away from the construction area
  • Unused land has been reinstated to a natural shape in Winstone Park
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