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New lanes ready for use on SH20


Motorists will get to drive on the newly constructed motorway lanes south of Mangere Bridge on the Southwestern Motorway from next week.

Motorists will get to drive on the newly constructed motorway lanes south of Mangere Bridge on the Southwestern Motorway [SH20] from next week.

Southbound traffic will shift to the new lanes to enable the Manukau Harbour Crossing project to open up a new construction zone in the middle of the motorway. 

The southbound lanes will be closed overnight on Sunday May 10 to prepare for the shift.  The work will be shifted to overnight on Monday 11 May or Tuesday 12 May if weather on Sunday prevents it going ahead.

There will be lane closures for northbound traffic on the same night, to allow for work on the new Rimu Road overbridge.  However, one northbound motorway lane will remain open at all times.

The detour for southbound traffic will be via the Mahunga Drive, and motorists are advised to allow extra time for trips to the airport. The motorway will be fully operational again from 5am following the overnight closure.

The NZ Transport Agency’s Auckland/Northland regional director, Wayne McDonald, says the traffic switch marks an important milestone for the Manukau Harbour Crossing project. He says the overnight closure is essential to ensure the continued safe operation of the Southwestern Motorway.  “Regular users of the motorway are now very familiar with the detour on this section of motorway and know it adds only minutes to trips to the airport.”

Under the Manukau Harbour Crossing project, the capacity of the Southwestern Motorway is being doubled between Queenstown Road in Hillsborough and Walmsley Road in Mangere to cope with traffic forecast to increase to 150,000 vehicles a day.  This includes duplicating the Mangere Bridge and widening the motorway either side of the bridge to three traffic lanes and a bus priority lane in each direction.

The NZTA plans to complete the project in early 2011, before the Rugby World Cup.

The next major milestones on the project will be the completion of the new Rimu Road overbridge and the Hastie Avenue footbridge – both expected in June 2009.

The NZ Transport Agency thanks motorists for their patience and co-operation while construction takes place.

For more information on the SH20 Manukau Harbour Crossing project, phone 0800 SH20 MHX (0800 7420 649) or visit link)

For more information please contact:

Ewart Barnsley
Communication & Stakeholder Manager
NZ Transport Agency
Ph 09 368 2142 or 027 213 7616