State Highway 18
Route information
Maintained by NZ Transport Agency
Length	14 km (8.7 mi)
Major junctions
North-east end	SH 1 (Auckland Northern Motorway) at North Shore
South-west end	SH 16 south (Northwestern Motorway) at West Harbour
Location
Country	New Zealand
Primary destinations	Greenhithe, Hobsonville
Highway system
New Zealand state highways Motorways and expressways List
← SH 17 → SH 20

State Highway 18 (SH 18) is a state highway that runs between the Auckland Northern Motorway (SH 1) on the North Shore and the Northwestern Motorway (SH 16) in West Auckland, New Zealand. The Upper Harbour Motorway forms most of its length as of 2016 (the exception being a two-kilometre stretch at the north-eastern end). SH 18 forms the northern part of the Western Ring Route, which continues from Waitakere south-east to Manukau.

Route

SH 18 begins at the Auckland Northern Motorway and runs southwest as a dual carriageway road, and is coextensive with the Upper Harbour Highway, which after two kilometres becomes a motorway at the Albany Highway interchange. This four-lane section of motorway opened in December 2007, and bypassed the single carriageway Upper Harbour Drive. The motorway heads south-west, crossing the upper reaches of the Waitematā Harbour over the Upper Harbour Bridge. 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.

Interchanges

Territorial authority	Location	km	mi	Exit	Destinations	Notes
Auckland – Upper Harbour Local Board	Unsworth Heights	0.0	0.0		SH 1 south (Northern Motorway) – Auckland	SH 18 begins
					SH 1 north (Northern Motorway) – Whangarei
		0.5	0.31	1	Caribbean Drive Paul Matthews Road	Eastbound exit and westbound entrance
		2.4	1.5	2	Albany Highway (Urban Route 26)	Upper Harbour Motorway begins
	Greenhithe	4.3	2.7	4	Greenhithe Road	Westbound exit and eastbound entrance
		6.2	3.9	6	Tauhinu Road	Eastbound exit and Westbound entrance
		7.4	4.6	Upper Harbour Bridge (Waitematā Harbour)
	Hobsonville	8.8	5.5	8	Squadron Drive	Westbound exit and eastbound entrance
		10.7	6.6	9	Brigham Creek Road – Whenuapai, Wellsford	to SH 16 north
		12.7	7.9	10	Trig Road	Westbound exit and eastbound entrance
Auckland – Henderson-Massey Local Board	Westgate	13.9	8.6	11	Hobsonville Road (Urban Route 32)	Westbound exit and eastbound entrance
		14.0	8.7		SH 16 south (Northwestern Motorway) – Waitakere, Auckland	SH 18 ends Upper Harbour Motorway ends
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

Former route

SH 18 formerly ran along the Coatesville Riverhead Highway, further north than its current position. This route is now designated as Auckland Urban Route 28.

Cycleway

The route of the new motorway from Upper Harbour Bridge to Westgate was originally to receive a cycleway as well, but although the land was set aside, there is no timetable for the construction of the route.^[1]