New Zealand State Highway 20

State Highway 20

Southwestern Motorway

Route information

Maintained by NZ Transport Agency

Length:

25 km (16 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:

SH 16 Northwestern Motorway at Point Chevalier

Highway system

New Zealand state highways

←

SH 18

SH 21

→

Aerial view of the interchange between SH 20 (diagonal from bottom left to upper right) and SH 20A 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 State Highway 16 in Point Chevalier, 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 kilometres (30 mi) motorway route bypassing central Auckland. It is the only New Zealand State Highway that is entirely motorway.

Route

SH 20 stretches from the Auckland Southern Motorway (SH 1) at Manukau to SH 16 at Point Chevalier. From south to north the motorway passes through, or adjacent to, the suburbs of Wiri, Mangere, Onehunga, Hillsborough, Mount Roskill, Mount Albert, Waterview and Point Chevalier.

The final terminus is Northwest Motorway (SH 16) via the Waterview Connection which opened in July 2017.^[1]

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, officially terminating at the intersection with Orrs Road. SH 20A 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. A construction project is underway in 2015–17 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.^[2]

History

The first section of what would become the Southwestern Motorway was the Onehunga Bypass from Queenstown Road in Hillsborough to Neilson Street in 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 in 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.^[3]

The southern section was extended to Puhinui Road in 1997, along with the extensions SH 20A and SH 20B connecting to Auckland International Airport. The final southern section connecting Puhinui Road to State Highway 1 at Manukau was completed in 2010.^[4] A duplication of Mangere Bridge, with future provision for rail, was also opened in 2010.^[5]^[6]

The final section of the Southwestern Motorway, the Waterview Connection, connecting Maioro Street with State Highway 16 at the Great North Road Interchange commenced construction in 2012 and opened to traffic in July 2017.^[1]^[7]

Exit list

Territorial authority	Location	km	Exit	Destinations	Notes
Auckland — Otara-Papatoetoe/Manurewa Boards	Manukau CBD	0.0	1	SH 1 Southern Motorway south — Hamilton, Tauranga	SH 20 and Southwest Motorway begins
		0.0	1	SH 1 Southern Motorway north — Auckland	SH 20 and Southwest Motorway begins
			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	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	SH 20A — Airport	Right-hand southbound exit and northbound entrance. No southbound entrance (use SH20B or Massey Road)
			10	Walmsley Road	Southbound
			10	Coronation Road	Northbound
	Mangere Bridge		12	Mahunga Drive — Mangere Bridge	Southbound exit and northbound entrance
	Mangere Bridge			Mangere Bridge over Manukau Harbour
Auckland — Maungakiekie-Tāmaki Board	Onehunga			Mangere Bridge over Manukau Harbour
	Onehunga		13	Neilson Street — Onehunga Wharf, Onehunga, Penrose, Mt Wellington
	Hillsborough		15	Route 12 Queenstown Road — Epsom, Royal Oak, Auckland CBD	Northbound exit and southbound entrance
Auckland — Puketāpapa Board			15	Route 12 Queenstown Road — Epsom, Royal Oak, Auckland CBD	Northbound exit and southbound entrance
			16	Route 15 Hillsborough Road - Hillsborough, Blockhouse Bay
	Mount Roskill		18	Route 4 Dominion Road - Mount Roskill
	Mount Roskill	19.7	19	Maioro Street - New Lynn, Sandringham	Waterview Connection begins
Auckland — Albert-Eden Board	Waterview	23.8	24A	SH 16 Northwestern Motorway west — Helensville, Wellsford	SH 20 and Southwest Motorway ends Waterview Connection ends
Auckland — Albert-Eden Board	Waterview	23.8	24B	SH 16 Northwestern Motorway east — Auckland
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

References

1 2 "Waterview Connection". NZTA.
↑ "SH20A to Airport". NZ Transport Agency. Retrieved 10 December 2016.
↑ Dearnaley, Mathew (18 May 2009). "Another piece slots into city's commuter jigsaw". The New Zealand Herald. Retrieved 5 March 2010.
↑ "SH20-1 Manukau Extension". NZTA.
↑ "Western ring route progressing". The New Zealand Herald. 7 June 2010. Retrieved 9 July 2010.
↑ "Mangere Bridge Opened Today". The New Zealand Herald. 25 July 2010. Retrieved 1 August 2010.
↑ "Auckland's Waterview Tunnel open to traffic at last". Stuff.co.nz. 2 July 2017. Retrieved 2 July 2017.

New Zealand state highways
List of New Zealand state highways List of unused highways in New Zealand List of motorways and expressways in New Zealand
National	SH 1 (incl. SH 1B, SH 1D) SH 2 (incl. SH 2B) SH 3 (incl. SH 3A) SH 4 SH 5 SH 6 (incl. SH 6A) SH 7 (incl. SH 7A) SH 8 (incl. SH 8A, SH 8B)
North Island	SH 10 SH 11 SH 12 SH 14 SH 15 SH 16 SH 18 SH 20 (incl. SH 20A, SH 20B) SH 21 SH 22 SH 23 SH 24 SH 25 (incl. SH 25A) SH 26 SH 27 SH 28 SH 29 (incl. SH 29A) SH 30 (incl. SH 30A) SH 31 SH 32 SH 33 SH 34 SH 35 SH 36 SH 37 SH 38 SH 39 SH 41 SH 43 SH 44 SH 45 SH 46 SH 47 SH 48 SH 49 SH 50 (incl. SH 50A) SH 53 SH 54 SH 56 SH 57 SH 58
South Island	SH 60 SH 62 SH 63 SH 65 SH 67 (incl. SH 67A) SH 69 SH 71 SH 73 SH 74 (incl. SH 74A) SH 75 SH 76 SH 77 SH 78 SH 79 SH 80 SH 82 SH 83 SH 84 SH 85 SH 86 SH 87 SH 88 SH 90 SH 93 SH 94 SH 95 SH 96 SH 97 SH 98 SH 99
Former state highways	SH 1A SH 2A SH 15 SH 15A SH 17 SH 36 SH 40 SH 47A SH 49A SH 52 SH 57A SH 61 SH 70 SH 72 SH 73A SH 89 SH 91 SH 92
Touring routes	Twin Coast Discovery Highway Thermal Explorer Highway Pacific Coast Highway Classic New Zealand Wine Trail Alpine Pacific Triangle Great Alpine Highway Foothills Scenic Route Inland Scenic Route Southern Scenic Route

List of motorways and expressways in New Zealand
Auckland	Northern Motorway Northwestern Motorway Southern Motorway Southwestern Motorway Upper Harbour Motorway
Wellington	Johnsonville–Porirua Motorway Wellington Urban Motorway Hutt Expressway Kapiti Expressway
Rest of North Island	Waikato Expressway Takitimu Drive Tauranga Eastern Link Hawke's Bay Expressway
South Island	Christchurch Northern Motorway Christchurch Southern Motorway Christchurch-Lyttelton Motorway Dunedin Southern Motorway
Past motorways/expressways	New Plymouth Southern Motorway Wanganui Metropolitan Motorway Dunedin Northern Motorway
Future motorways/expressways	Puhoi to Wellsford Motorway Penlink Second Harbour Crossing Transmission Gully Motorway Western Belfast Bypass
Major infrastructure	Upper Harbour Bridge Northern Busway, Auckland Auckland Harbour Bridge Victoria Park Tunnel and Viaduct Central Motorway Junction Newmarket Viaduct Mangere Bridge Tauranga Harbour Bridge Ngauranga Interchange Terrace Motorway Tunnel Lyttelton Road Tunnel Waterview Tunnel

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