Transit New Zealand



Completion date


Marshall Day Acoustics was engaged by Beca Carter Hollings & Ferner on behalf of 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 its 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.


Our Brief

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 Highway containing hundreds of dwellings and apartments. Future traffic noise levels were predicted for a large number of individual dwellings for multiple options of traffic lane combinations including various at grade, viaduct 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 road projects. Marshall Day Acoustics' work on this project, including the computer modelling was peer reviewed by Richard Heggie Associates, Lane Cove, NSW.