The New Zealand Transport Agency has signed a contract with Leighton Contractors to upgrade a 2km stretch of State Highway16 (Northwestern Motorway) in Auckland.

Under the NZ$70m ($58m) contract, Leighton Contractors widen the motorway from three to four lanes in each direction from the St Lukes Road interchange in Western Springs to the Great North Road interchange in Waterview.

The contract will also see the infrastructure company making improvements to ramps and the motorway overbridge at the St Lukes Interchange.

"We look forward to contributing our experience from similar projects both here and overseas."

These new layout and additional lanes are expected to ease congestion and improve safety in the region.

The new project is part of the the NZ Transport Agency’s Western Ring Route that will offer an alternative motorway connection between Manukau City and Albany, bypassing Auckland’s city centre and the Auckland Harbour Bridge.

Leighton Contractors New Zealand general manager Andrew Stevens said: "This is a vital section of the Western Ring Route, which when complete, will significantly improve access and connectivity for Auckland’s commuters and freight carriers.

"Working with the Transport Agency, we look forward to contributing our experience from similar projects both here and overseas."

In the recent past, Leighton Contractors has secured several major road development contracts including the Northern Gateway Toll Road, SH20 Manukau Motorway Extension and Newmarket Viaduct replacement project.

The Wellington Gateway Partnership (WGP), led by Leighton Contractors, was recently appointed by the NZTA as preferred proponent to deliver the NZ$1bn ($829m) Transmission Gully Motorway, under Public Private Partnership arrangement.