Victoria Park Tunnel (VPT) is the third of three priority projects - known collectively as the Central Motorway Improvements - to be recently undertaken in central Auckland. 

Their aim is to improve the overall efficiency and safety of the central motorway system by better managing traffic flows and addressing congestion.  VPT is the final project and addresses the bottleneck between the Central Motorway Junction and the Auckland Harbour Bridge.

Since 1996, the New Zealand Transport Agency has been looking at ways to improve traffic flows through this heavily congested section of motorway. Improvements to this section are essential in order to realise the full capacity of the Auckland Harbour Bridge, and to obtain the benefits of the nearly completed Central Motorway Junction and the completed Grafton Gully motorway projects. The project will also allow the North Shore Busway to meet its full potential.  Without the improvements the existing traffic flow will continue to be constrained.

Marshall Day Acoustics was engaged by Beca Carter Hollings & Ferner on behalf of NZTA (then Transit New Zealand) to examine the potential traffic noise effects of a proposal to upgrade State Highway 1 between Auckland City Central Business District and the Harbour Bridge.  This 2 km section of highway generally carries the highest traffic volume of any road in New Zealand and the overall object is to increase its capacity so as to enable maximum vehicle flows on the Harbour Bridge.

Marshall Day Acoustics' function was to examine all aspects of the potential traffic noise generation and its mitigation to meet the Transit Guidelines and other criteria. This involved extensive surveys of the existing ambient noise levels for a large area to the south of the Harbour Bridge containing hundreds of dwellings and apartments.

Future traffic noise levels were predicted for a large number of individual dwellings for all residential floors and for multiple options of traffic lane combinations including various 'at grade', 'trench' and 'tunnel' scenarios.  Each option was assessed for overall noise impact and viable mitigation measures including road surface specification and various traffic noise barrier arrangements.

The barrier proposals included a variety of materials of construction including transparent alternatives to preserve harbour views for affected residents.  Traffic noise levels were predicted, and mitigation options evaluated using the traffic noise modelling capabilities of SoundPLAN.  The SoundPLAN program proved to be a powerful tool for these combinations of carriageway, and mitigation alternatives.  Marshall Day Acoustics' consultants have developed a high degree of facility and productive capability with the use of SoundPLAN on this and many other major roading projects.