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SH20 Walmsley upgrade project

SH20 is a key section of the Western Ring Route, a Road of National Significance that will deliver economic benefits and development along the corridor, in particular west and southwest Auckland. The Walmsley upgrade works will contribute to the regional benefits created by the upgrade of this important link.

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Aerial view of Walmsley Road interchange..

Aerial view of Walmsley Road interchange.

Auckland

  • Part of

    Western Ring Route

  • Construction start date

    October 2010

  • Construction completion date

    September 2011

  • Location

    Walmsley Road Interchange, Southwestern Motorway (SH20), Auckland

  • Project type

    Roads of national significance

  • Project status

    Construction

  • Project contact

    Marcus Lin

  • Estimated cost

    $5 million to $20 million

Project purpose

Over the next year, the NZ Transport Agency and its partners forming the Manukau Harbour Crossing Alliance will be undertaking road widening works and other improvements on the South-western motorway (SH20) at the Walmsley Road interchange.

Currently, SH20 comprises of three southbound lanes from Queenstown Road, and then reduces to two lanes south of Walmsley Road prior to the split to SH20 and SH20A. This presents a 'bottleneck' that is anticipated to get worse in the next few years, posing safety and congestion issues. There are already signs of traffic slowing down and doing dangerous weaves.

Traffic using the Walmsley Road on-ramp heading to SH20A (the airport route) is another issue of concern. There is limited distance to cross lanes and increasing traffic volumes will cause conflict between vehicles wanting to change lanes and those going straight ahead. This is likely to increase accidents and congestion on the motorway.

Widening the motorway and adding one more southbound lane will solve the bottleneck issue.

However traffic from Walmsley Road on-ramp would then need to cross two lanes to reach SH20A. There is not enough room to change lanes safely, so a barrier will be built next to the on-ramp to prevent this.

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Benefits

  • No bottleneck will mean the traffic will be able to continue to flow freely
  • Cutting off access to SH20A from the Walmsley on-ramp will stop vehicles from having to weave across lanes and therefore make it much safer
  • There will be a decrease of accidents and congestion on the motorway in this area
  • As this is part of the Western Ring Route travel times to Manukau and the Auckland International Airport will be more reliable.

Features

  • A third lane southbound
  • Realigning and lengthening of the Walmsley Road on-ramp
  • Building a barrier next to the Walmsley Road on-ramp to prevent vehicles from crossing to SH20A (to the Auckland Airport)
  • Lengthening the Hall Ave foot bridge to fit over the widened motorway
  • Widening the South Grade Line Bridge at the southern end
  • Building a new noise wall along the length of SH20 (southbound side)
  • Landscaping.

Other facts

Alternate routes for travel to SH20A:

Due to safety concerns, movement from the Walmsley Road on-ramp to SH20A will be stopped from about February 2011. Alternative routes for traffic heading to SH20A from this area, include:

  • Travelling further south on SH20 and exiting at Massey Road
  • Travelling further south on SH20 and exiting at Puhinui Road (SH20B)
  • Travelling via McKenzie and Kirkbride Roads, which is already a sign posted route to the airport

The NZ Transport Agency anticipates that any potential traffic effects of the diversion will be no more than minor. We will put a monitoring program in place to ensure that there are no significant impacts on the state highway or local network, and long term planning will consider other transport improvements.

Hours of work: Most work will be done during the day, Monday to Friday. Work in the weekend and at night maybe required from time to time. We commit to informing directly affected residents if such hours of work are required.

Vegetation removal: All the planting and vegetation will be removed alongside the motorway to make room for construction works. The edge of the motorway will be replanted where possible.

Earthworks, Noise, Vibrations and Dust: During construction there may be temporary additional noise, vibration or dust. We commit to doing whatever we can where ever we can to minimise disturbance.

Hall Avenue Foot Bridge: The Hall Avenue Foot Bridge will be lengthened to fit over the widened motorway. Access across the foot bridge will be maintained during these works. The community will be given advance notice if the access arrangements change.

Delivered by: The Manukau Harbour Crossing Alliance comprising NZ Transport Agency, Fletcher Construction, Beca Infrastructure & Higgins Contractors.