State Highway 18 (New Zealand)

SH 18 forms the northern part of the Western Ring Route, which continues from Waitakere south-east to Manukau.

This four-lane section of motorway opened in December 2007, and bypassed the single carriageway Upper Harbour Drive.

At Squadron Drive, the highway extends onto a new section of motorway, which opened in August 2011, bypassing Hobsonville Road.

[1] This road cuts across in a southwestern direction across farmland to Westgate, where it turns southward and merges with the Northwestern Motorway (SH 16) southbound.

SH 18 formerly ran along the Coatesville Riverhead Highway, further north than its current position.

The former route of State Highway 18, in 2010, was a mostly rural highway. This route is now designated Urban route 32.
The Hobsonville section of the Upper Harbour Motorway, looking west from the Trig Road Interchange