Leighton Contractors has secured a $267m contract from the New Zealand (NZ) Transport Agency to upgrade Auckland’s Southern Corridor to improve traffic flows on State Highway 1 between Manukau and Papakura.

The project is one of four government accelerated transport projects for the Auckland region and the transport agency’s second to be delivered following the State Highway 20A to Airport project.

Work will include southbound widening to four lanes between SH20 and Hill Road and to three lanes between Hill Road and Papakura, as well as northbound widening to three lanes from Papakura to Takanini.

"The project is one of a range of improvements being developed to address growth and demand within and south of Auckland."

In addition to construction of additional lanes, the project also involves upgrading 16 bridges and constructing six new bridges.

The project also includes a new 4.5km walking and cycleway, as well as new LED lighting.

NZ Transport Agency state highways manager for Auckland and Northland Brett Gliddon said: "The Southern Corridor is a key route from the north, connecting Auckland to the Waikato, Bay of Plenty and the rest of New Zealand.

"The project is one of a range of improvements being developed to address growth and demand within and south of Auckland by helping to move people and freight more efficiently."

The project will connect Manukau and the North Shore through State Highway 20 (the Waterview tunnel) and State Highways 16 (the Northwestern) and State Highway 18, as an alternative North-South route to State Highway 1.

Work is scheduled to start in October and is expected to be opened in stages ahead of its 2018 completion target.

The completion of the project will see more consistent journey times on the Southern Motorway, improved traffic flow and connections between the local roads and state highway to help ease congestion.