Transmission Gully motorway is a key part of the Wellington Northern Corridor ‘Roads of National Significance’. Built to demanding specifications, the design and construction of Transmission Gully motorway reflects the need for an alternative route between Wellington and the lower and central North Island that will be both quicker and safer for motorists and more resilient to earthquakes and storms.

The 27km four-lane motorway and its 27 new structures will be built to withstand very large earthquakes and provide a brand new route between Linden and Mackays Crossing, near Paekakariki.

The project is highly complex, with difficult and steep terrain requiring large-scale earthworks that will see approximately 6.5 million cubic metres of earth moved during construction of the project. 27 new structures equating to a total length of 1.2km will be constructed along the route. The largest of these, the Cannons Creek Bridge, will stretch 230m in length and sit 60m above the valley floor.

The Transmission Gully motorway is scheduled to be open for traffic in 2020.

First of its kind

Transmission Gully is the first motorway in New Zealand to be constructed on behalf of the New Zealand Government under a Public Private Partnership (PPP) contract. In July 2014 the NZ Transport Agency signed a PPP contract with the Wellington Gateway Partnership (WGP), a private consortium of financiers and contractors, to design, construct, finance, and then operate and maintain the new motorway for 25 years following the scheduled five year construction period. WGP has contracted a joint venture of CPB Contractors (formerly Leighton Contractors) and HEB Construction (CPB HEB JV) to undertake the motorway design and construction.