Hobsonville motorway enables future growth

The striking Clarks Lane ‘canary bridge’ – one of the most visual aspects of the urban design programme for the Hobsonville Deviation

The Prime Minister and the NZ Transport Agency have opened the latest component of Auckland’s Western Ring Route, one of the government’s seven roads of national significance, providing a motorway alternative to SH1 and excellent prospects for future development around the upper reaches of the Waitemata Harbour.

Opened six months ahead of schedule on 6 August, the $220 million Hobsonville project has two components: the Hobsonville Deviation, a 6 km, four-lane motorway that runs between the Upper Harbour Bridge at Greenhithe to the east and the Northwestern Motorway (SH16) in the west; and the Brigham Creek Extension, a 3 km, four-lane extension of SH16 from Westgate to a new roundabout at Brigham Creek Road just short of the Kumeu township.

The new motorway connects the North Shore with west Auckland; up to 35,000 vehicles are expected to use the new Hobsonville route each day, with 14,000 on the Brigham Creek route. The former provides a muchneeded alternative to the speed-restricted, accident-prone Hobsonville Road, New Zealand’s sixth worst road for fatalities and crashes – indeed, traffic is expected to reduce by 80% along this route.

The NZTA’s state highways manager for Auckland and Northland, Tommy Parker, says: “The completion of the Hobsonville project is part of a transport solution that provides benefits to New Zealand, the Auckland region, and the communities living close to the motorway. It will help open up access and pro - vide the transport backbone for the developing areas of northwest Auckland, and at the same time improve safety by taking thousands of vehicles off the old state highway along Hobsonville Road.”

Long history

In 1961, the four-lane Northwestern Motorway (SH16) was opened from Point Chevalier to Hobsonville Road to service Auckland’s original airport at Whenuapai. In 1966, the Auckland International Airport was opened at Man - gere, and Whenuapai reverted to a military airport.

Motorway ramps into the CBD were completed between 1977 and 1979, with links to Grafton Gully and the Southern Motorway heading south completed in 1988 and 1989. The growth of Auckland’s western suburbs during the 1980s and the establishment of Waitakere City in 1989 led to escalating numbers of commuters, and during the 1990s, several sections of the motorway were widened to six lanes, with new interchanges built.

Meanwhile, on the North Shore, Albany was also growing as an urban hub, and with state highway status conferred on Hobsonville Road in 1991 (SH18), work began on improving capacity along Upper Harbour Drive to link the North Shore with west Auckland.

The original Upper Harbour Bridge was completed at Greenhithe in 1975. A second cantilevered bridge was constructed adjacent to the original, and opened to traffic in 2006. By this time, construction was well underway on the SH18 Greenhithe Deviation, a four-lane motorway between the Upper Harbour Bridge and the Albany Highway. This was officially opened in December 2007.

The new Hobsonville Deviation, plus the extension to Brigham Creek Road, is the last stage of the total SH18 Upper Harbour Motorway. It too has a number of new interchanges, with a sweeping flyover at what used to be the end of the Northwestern Motorway, and there is provision for bus shoulder lanes on each side of the motorway in the future.

Park-like landscape

Much of the area comprises native bush and natural farmland, and Mr Parker says they have endeavoured to preserve the park-like landscape as much as possible, working closely with both Waitakere and North Shore City councils of the time and later Auckland Council, with input from local artists and architects for the design of bridges, noise walls and other structural features.

The most visual aspect of this urban design programme is the striking ‘canary bridge’, a bright-yellow cable-stayed 60 m footbridge, which was opened to pedestrians and cyclists in October 2010. The bridge has a 24 m high central pier which anchors the cables. Tiles made by local artists from a variety of clays that were part of an extensive pottery and brick-making industry in the area have been laid on the deck of the bridge, and a windows sculpture has been erected alongside. This work, by Waitakere artist John Radford, includes windows preserved from the original Sinton House homestead in Hobsonville, which had to be demolished as it could not be relocated for the motorway project.

In addition, timber noisescreening walls along the motorway have been painted bright orange by Auckland Council, and feature a ‘tyre track’ design installed by Waitakere artist Jeff Thomson. These have been used where residential homes are sited close to the motorway to limit noise and provide a degree of privacy from passing motorists.

Innovative construction

Principal contractor, HEB Construction, and project designer, Aurecon, have used a number of innovative construction techniques as part of the project. Steve Croft, HEB project manager, points out the intricacies of the interchange at the end of the Northwestern Motorway.

“This was a very demanding project – its ten lanes wide, and includes the on-ramps and off-ramps for Hobsonville Road and the continuations for SH18 and SH16. We had to dig out the earth below Hobsonville Road to turn it into a bridge, all the time keeping it open to traffic.”

Extensive earthworks were required to convert the rolling pastures and bush-clad hills into a smooth motorway surface. “The project involved 1.4 million cu m of earthworks and 350,000 sq m of pavement construction. We’ve used over 196,000 tonnes of asphalt on this project – it’s currently the biggest asphalt job in New Zealand,” Steve says. “

We’ve made extensive use of stormwater treatment ponds to filter runoff, with the added bonus that we’ve cre - ated ponds for local fauna.” Over 400,000 natives have been planted along the verges and earthwork banks.

HEB was awarded the NZ Contractors’ Federation Environmental Award in 2010 (Category 4 – projects over $10 million) for the Hobsonville Deviation.

One step closer

Tommy Parker says the new motorway will open up parts of west and north Auckland for much-needed commercial and residential development. For example, work on the planned Westgate Town Centre is now underway. Located just off the Hobsonville Road/ SH18 interchange, close to Westgate, it will include the Massey library, community centre, retail services, medical services, cinemas and entertainment facilities.

Direct access from the motorway to the new Hobsonville Point housing development, on the old Hobsonville Aerodrome site, is also now available, made possible with the creation of the SH18 Squadron Drive Interchange. The development, in its early stages, aims to build 3000 residential houses, new primary and secondary schools and community facilities progressively over the next 10–15 years.

“The roads of national significance projects were identified as those that will support and enable economic growth for the benefit of the entire country,” Mr Parker says. “The SH18 Hobsonville Deviation and SH16 Brigham Creek Extension complete the northern stretch of the Western Ring Route road of national significance and bring the finish of the motorway one stage closer to being completed by 2021. The Western Ring Route will improve connections between Manukau in the south, Auckland International Airport, Waitakere and the North Shore, and ease congestion on the Auckland Harbour Bridge.”

The NZTA is due to start construction on the final section of the route – the Waterview Connection – later this year. Capacity improvements are also planned for the Northwestern Motorway and associated interchanges.