New Zealand State Highway 20

State Highway 20
Southwestern Motorway
Route information
Maintained by New Zealand Transport Agency
Length:	19 km (12 mi)
Existed:	1977 – present
Major junctions
South end:	SH 1 Southern Motorway at Manukau City Centre
	SH 20B at Puhinui SH 20A at Mangere
North end:	Sandringham Road/Maioro Street at Mount Roskill
Highway system
New Zealand state highways Motorways and expressways List Unused ← SH 18 SH 21 →

File:SH20-SH20A Interchange In Mangere.jpg

Aerial view of the interchange between SH20 (diagonal from bottom left to upper right) and SH20A towards the airport (towards bottom right).

State Highway 20, also known as the Southwestern Motorway, is a New Zealand State Highway linking State Highway 1 at Manukau City Centre with Mount Roskill, via Mangere and Onehunga. Along with its spurs, State Highway 20A and 20B, the state highway serves Auckland Airport, the country's largest, therefore making State Highway 20 a key arterial route connecting the airport to the wider Auckland region and most of the upper North Island. The route also forms the southern part of the Western Ring Route, a 48 km motorway route bypassing central Auckland.

Route

SH 20 stretches from the Auckland Southern Motorway / New Zealand State Highway 1 at Manukau to Sandringham Road, Sandringham, in Auckland City. From south to north the motorway passes through, or adjacent to, the suburbs of Wiri, Mangere, Onehunga, Hillsborough and Mount Roskill.

The motorway (and SH 20) currently terminates at Maioro Street. The planned final terminus will be the Northwest Motorway / New Zealand State Highway 16 via the Waterview Connection scheduled to open in 2017.

Airport connection

SH 20, SH 20A, and SH 20B form an almost triangular shape between the Puhinui Interchange of the Southwestern Motorway, Auckland International Airport, and the SH 20/SH 20A motorway junction. The Southwestern Motorway bypasses Auckland International Airport, with spurs SH 20A from the north and SH 20B from the east both providing airport access.

SH 20B leaves SH 20 at the Cavendish Dr/Puhinui Rd/Roscommon Rd Interchange of the Southwestern Motorway and travels west along Puhinui Road to the airport. SH 20B officially terminates at the intersection with Orrs Road. SH20A leaves the Southwestern Motorway in Mangere and travels south along an additional stretch of motorway, commonly referred to as the "Airport Motorway". The motorway terminates at Kirkbride Road, and traffic continues on SH 20A terminating just north of the roundabout with Verissimo Drive. From there the road continues south to the airport. NZTA are currently planning to turn SH 20A into a motorway for its entire length by turning the intersection at Kirkbride Road (and a known black spot) into a grade-separated intersection.

History

The first section of what would become the Southwestern Motorway was the Onehunga Bypass from Queenstown Road, Hillsborough to Neilson Street, Onehunga but the start of the motorway proper was not completed until 1983 when the bypass was connected through the new Mangere Bridge to Coronation Road, Mangere.

The northern section was extended first to Hillsborough Road, then to Hayr Road, then to Maioro Street, the last section opening on 15 May 2009.

The southern section was extended to Puhinui Road in 1997, along with the extensions SH20A and SH20B connecting to Auckland International Airport. The final southern section connecting Puhinui Road to State Highway 1 at Manukau was completed in 2010. A duplication of Mangere Bridge, with future provision for rail, was also opened in 2010.

Future

The final section of the Southwestern Motorway, the Waterview Connection, will connect the current western terminus of State Highway 20 at Maioro Street with State Highway 16 at the Great North Road Interchange. Construction of this section began in 2012 and is due for completion in 2017.

Proposals to upgrade State Highway 20A as part of a general route upgrade to the airport have been floated in a number of studies.

Exit list

Territorial authority		Location	km	Exit	Destinations	Notes
Former	Current (from 1 Nov 2010)
Manukau City	Auckland — Otara-Papatoetoe/Manurewa Boards	Manukau CBD	0.0		SH 1 Southern Motorway south — Hamilton, Tauranga	SH 20 and Southwest Motorway end
				1	SH 1 Southern Motorway north — Auckland
				2	Lambie Drive — Manukau, Wiri
		Puhinui		3	Route 30 Cavendish Drive/Roscommon Road - Manukau, Wiri	No southbound exit (use Puhinui Road) Northbound entrance and connection to SH 20B and
	Auckland — Otara-Papatoetoe Board	Puhinui		3	20px SH 20B Puhinui Road — Airport, Papatoetoe	No northbound exit (use Cavendish Drive) Southbound entrance and connection to SH 20B and
	Auckland — Mangere-Otahuhu Board	Mangere		7	Route 14 Massey Road - Mangere
				9	20px SH 20A — Airport	No southbound entrance (use SH20B or Massey Road) Carriageway mainline connects north to west, traffic proceeding from/to south on motorway must 'exit'.
				10	Walmsley Road	Southbound
					Coronation Road	Northbound
		Mangere Bridge		12	Mahunga Drive — Mangere Bridge	Southbound exit and northbound entrance
					Mangere Bridge over Manukau Harbour
Auckland City	Auckland — Maungakiekie-Tāmaki Board	Onehunga
				13	Neilson Street — Onehunga Wharf, Onehunga, Penrose, Mt Wellington
	Auckland — Maungakiekie-Tāmaki/Puketapapa Boards	Hillsborough		15	Route 12 Queenstown Road — Epsom, Royal Oak, Auckland CBD	Northbound exit and southbound entrance
	Auckland — Puketapapa Board			16	Route 15 Hillsborough Road - Hillsborough, Blockhouse Bay
		Mount Roskill		18	Route 4 Dominion Road - Mount Roskill
			19.7		Maioro Street - New Lynn, Sandringham	SH 20 and Southwest Motorway end
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

See also

• List of motorways, expressways, and highways in Auckland

External links

• "Mangere Bridge Opened Today". The New Zealand Herald. 25 July 2010. Retrieved 1 August 2010.