Central Motorway Junction, Auckland, New Zealand

The Central Motorway Junction project in New Zealand will link the Northern Motorway to Auckland’s port and North-Western Motorway. The works on the project, being developed in two stages at an investment of NZ$195m, began in October 2002 and the completion is due in January 2007.

Located in the heart of Auckland’s motorway network, the Central Motorway Junction is a ‘T’ interchange between the Northern / Southern Motorways and the North-Western Motorway. The Central Motorway Junction is bound by Wellington Street to the north, Newmarket Viaduct to the south and Bond Street to the northwest. With over 200,000 vehicles passing through it daily, the Central Motorway Junction is one of the busiest ways in New Zealand. Generally, traffic volumes go up by about 80% during the peak hours when compared with the off-peak time.

Alongside establishing a new link between the Northern Motorway and Auckland’s port, the objectives of the project are to ensure safety standards and smooth traffic flow through the Spaghetti Junction interchange. Transit New Zealand, the state-owned road authority, which maintains the 10,894km of state highways in the country, is sponsoring the Central Motorway Junction project.

BACKGROUND AND DESIGN OF THE SCHEME

The planning for the Auckland motorway system began in 1955 with the release of the master transportation plan by the Auckland Regional Planning Authority. During the 1970s, various components of the Central Motorway Junction were built to provide links between the north, south and north-west.

Prior to the current two projects the engineering company Sinclair Knight and Merz (also retained to advise on the design and engineering for phase two) was commissioned to produce a report on the CMJ and how it could be improved. The report involved consultants from Halcrow and also Bloxham, Burnett and Olliver and was able to highlight the problems and some strategic solutions. The report suggested:

• Widening the main State Highway to provide two continuous lanes in each direction
• Constructing four new links including new viaduct structures
• Constructing a new viaduct structure for a revised off-ramp to the Central Business District (CBD)
• A braided ramp structure and associated link road connections at the northern limit of the project
• Widening of the existing southbound SH1 carriageway

A link between Karangahape Road area and Dominion Road was included in the original Central Motorway Junction design, but this link was not completed. Subsequently, a link from the North-Western Motorway to Grafton Gully was opened in 1988 and the link between the North-Western Motorway and the Southern Motorway was completed in 1989.

The other two motorways under construction in Auckland, the 'South-Western' and 'Upper Harbour' motorways, will form a continuous link in the west of the city between SH1 in the south at Manukau with SH1 in the north at Albany. The main goal of this new route is to provide an alternative relief north–south route in the west that bypasses the central area and avoids the often congested CMJ.

CENTRAL MOTORWAY JUNCTION STAGE ONE

Under stage one, undertaken by Freeflow, the route between Symonds Street and the Gillies Avenue section of the Southern Motorway was upgraded. The $55m upgrade works under stage one took 26 months for completion from the commencement of construction in October 2002.

As part of the upgrade works, major emphasis has been given to safety on this route, including the addition of a further southbound lane and improved lane configurations. Stage one also included an extra road width to accommodate future improvements. The storm water run-off treatment has been improved through a series of sand filters and catchpit filter bags to minimise surface flooding.

An extended merge area at the southbound Grafton on-ramp was provided to help heavy vehicles merge with the motorway traffic. A fourth southbound lane, by way of a two-lane off-ramp from Upper Queen Street to Gillies Avenue, has increased the capacity at the latter point for better queuing. A new northbound lane, from the Gillies Avenue on-ramp to the Khyber Pass off-ramp, is aimed at improving traffic flow.

The alignment of the Wellesley Street off-ramp northbound has also been improved, including seismic performance and structural upgrades for the Khyber Pass Viaduct, Grafton Bridge 2 and Grafton Bridge 3 A. Sufficient southbound carriageway width has been provided to accommodate a future ramp from Khyber Pass to the Gillies Avenue overpass.

CENTRAL MOTORWAY JUNCTION STAGE TWO

The core project under stage two, handled by a Complete Joint Venture (CJV) between Fletcher Construction and Leighton Contractors, is aimed at providing new connections between the Northern Motorway and Auckland’s port and the Northern Motorway and North-Western Motorway. The CJV began the $140m, stage-two construction works of the Central Motorway project in January 2004. This work is due to be completed by January 2007.

Stage two has been extended to include an upgrade of the Southern Motorway (SH1) southbound between the Cook Street off-ramp and the Hobson Street on-ramp. This extension work on the Southern Motorway southbound, known as the 'northern tie-in', will provide new links to exit from the SH1 on the left-hand side after the Cook Street off-ramp and before the Wellington Street bridge.

The new links have been designed to ensure smooth flow of traffic. The links will exit in a single lane from SH1 and then widen into two lanes so that slower traffic bound for the port can use the left lane. In June 2006 the new off-ramp from SH1 to Nelson Street was completed so that drivers can now exit the highway from the left, making it easier for drivers heading into the CBD. This involved the widening of the Southern Motorway north bound approach.

CONTRACTORS

Freeflow, an alliance between Transit New Zealand, Fletcher Construction Ltd, Beca Carter Hollings and Ferner Ltd and Higgins Contractors Ltd developed the stage one project. Beca Carter Hollings and Ferner provided design services. Beca entrusted the task of providing specialist design services to Parsons Brinkerhoff as a sub-consultant.

Under a service contract, the main contractor engaged URS New Zealand Ltd to provide verification of the design, while sub-contractors were engaged to perform demolition, earthworks, pavements, landscaping, and traffic-control implementation. The engineering and design consultants are responsible for the development of the Central Motorway Junction project.

Freeflow, in association with Transit NZ and the principal contractor, was responsible for stage one of the project. Freeflow is an alliance between Beca Carter Hollings & Ferner, Fletcher Construction and Higgins Contractors. The CJV between Fletcher Construction and Leighton Contractors, Australia, is developing stage two of the project.

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