Contents: History | Why an Upgrade? | Mangere Bridge Widening | Construction Images | Hillsborough to Walmsey Widening | Feedback Area

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The Mangere Bridge

The South Western Motorway (SH20) was constructed in stages during the late 1970's, early 1980's and late 1990's to provide more efficient connections to Auckland Airport and Manukau City and starting the long process of the still incomplete Western Ring Motorway Network.

The first section of the South Western Motorway started construction in late 1977, the section was only a short approach to the old Mangere bridge bypassing the busy Onehunga area. The present Mangere Bridge after a very long and negative construction process was completed in March 1983. It connected the already used Onehunga bypass to the newly completed crossing to create a total section between Neilson Street and Coronation Road of 1.8km.

Under construction in 1982

In 1997 the Coronation Road to Puhinui Interchange, and link to Kirkbride Road section was completed. The Mt Roskill Extension was completed on the 15th of May 2009, extending from Hillsborough Road to Maioro Street. Other projects on the South Western Motorway include the Waterview Connection project and the Manukau Extension Project.

This extension is one of the projects that is part of the Western Ring Motorway Network. The Western Ring motorway will offer a much needed alternative to the overloaded Northern and Southern Motorways.

Why Does it Need to be Widened?

Congestion: The present Mangere Bridge no longer meets the capacity of the South Western Motorway, with the growth of Auckland Airport and surrounding residential and industrial areas has meant the South Western Motorway is being used to the extent where congestion is created and desirable speeds are not met. Also commuters live on one side and work on the other meaning that there is significant short distance travel on the bridge and because the Mangere Bridge is the only harbour crossing it becomes congested.

Western Ring Motorway: Both ends of the South Western Motorway are to be extended to join the Southern and North Western motorways. There will be a significant increase in traffic on the South Western Motorway. This means the Mangere Bridge can become a pinch point that will need to be addressed.

The Mangere Bridge Duplication

Completed: 31st of August 2010 at $230m

The Mangere Bridge Widening will not widen the existing bridge but duplicate the existing one to the north east. This means they use a similar design and height and build it alongside the present Mangere Bridge. This duplication is the most cost effective mainly due to integration with the existing motorway.

To only widen the existing bridge it would require expensive large scale foundation and structural improvements, resulting in fewer lanes and would still suffer from the current sagging issues.

When the project is complete it will offer four lanes in each direction, double the current capacity. It will also include dedicated bus shoulder lanes in both routes. Provision is provided for extra widening in the future if needed.

Many people have expressed anger that the duplication does not include provision for rail, for a direct rail connection from Onehunga and the proposed Southdown rail network to Auckland Airport. This option may be resurrected. Eventually using a new single purpose bridge or the old Mangere Bridge.

In May 2010, traffic began using a third lane north, and on Monday the 26th of July 2010 three lanes were operational southbound on the new bridge.

Artists Impression of Duplicated Bridge

This image is © 2009 AucklandMotorways.co.nz. Satellite images from Google.

Construction Images

Above: Completed spans.

Above: Almost complete Mangere Bridge duplication, taken from the southern side. Three lanes are open on the existing bridge westbound.

Above: Sequenced image of the Mangere Bridge construction. Click for larger image.

Hillsborough to Walmsley Widening

Under construction | Completion: 31st of August 2010

From Hillsborough Road in the west until Walmsley/Coronation Road further south the South Western Motorway will be widened to three lanes.

This is the busiest section of the South Western Motorway as most traffic uses this part of the South Western for access to and from the Auckland Airport. This also ties in with the three lane widening of the Mangere Bridge.

The motorway will also be improved, to a better motorway standard addressing issues like the current dips, lane and shoulder width.

Currently three lanes are open southbound between Hillsborough Road and Neilson Street and Rimu Road and Walmsey Road. Three lanes are open westbound between the SH20a (airport) on-ramp and Hillsborough Road.

Above: Widening progress between Rimu Road and Coronation Road is complete, with three westbound lanes open on the Mangere bridge. Looking north.

Above: Widening progress between Rimu Road and Coronation Road is complete. Looking south.

Above: Widening between Queenstown Road and Neilson Street interchange complete. Before and after.

Above: Widening between Queenstown Road and Neilson Street interchange complete.