State Highway 20 (New Zealand)

State Highway 20 (SH 20), also known as the Southwestern Motorway, is a New Zealand state highway linking State Highway 1 at Manukau with State Highway 16 in Point Chevalier, via Māngere and Onehunga. Along with its spurs, State Highway 20A and 20B, the state highway serves Auckland Airport, the country's largest, therefore making SH 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.

State Highway 20
Southwestern Motorway
Route information
Maintained by NZ Transport Agency
Length25 km (16 mi)
Existed1977–present
Major junctions
South end SH 1 (Auckland Southern Motorway) at Manukau City Centre
  SH 20B (Puhinui Road) at Puhinui
SH 20A (George Bolt Memorial Drive) at Māngere
North end SH 16 (Northwestern Motorway) at Waterview
Highway system
← 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).

Route

SH 20 begins from the Auckland Southern Motorway (SH 1) at Manukau, then heads northwest to Māngere. It then runs over the Māngere Bridge to Onehunga, whereupon it continues northwest, cutting through Mount Roskill and Owairaka. It then enters the Waterview Tunnel, New Zealand's longest road tunnel,[1] before ending at a junction with the Northwestern Motorway (SH 16)

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 20A leaves the Southwestern Motorway in Māngere and travels south along an additional stretch of motorway, commonly referred to as the "Airport Motorway". The motorway passes underneath Kirkbride Road at a grade separated intersection which until 2017 was the former terminus for the motorway (and a known black spot).[2] The motorway continues south and terminates at the intersection with Verissimo and Landing Drives[3] where SH 20A also terminates. From there the road continues south, along George Bolt Memorial Drive, to the airport.

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.

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 Māngere.

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.[4]

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 SH 1 at Manukau was completed in 2010.[5] A duplication of Mangere Bridge, with future provision for rail, was also opened in 2010.[6][7]

The final section of the Southwestern Motorway, the Waterview Connection, connecting Maioro Street with SH 16 at the Great North Road Interchange commenced construction in 2012 and opened to traffic in July 2017.[1][8]

Exit list
Territorial authority Location km Exit Destinations Notes
Auckland — Ōtara-Papatoetoe/Manurewa Boards Manukau CBD 0.0 1 SH 1 south (Southern Motorway) — Hamilton, Tauranga SH 20 and Southwest Motorway begins
SH 1 north (Southern Motorway) — 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 — Ōtara-Papatoetoe Board SH 20B (Puhinui Road) — Airport, Papatoetoe No northbound exit (use Cavendish Drive)
Southbound entrance and connection to SH 20B and
Auckland — Māngere-Ōtāhuhu Board Māngere 7 Route 14 Massey Road – Māngere
9 SH 20A — Airport Right-hand southbound exit and northbound entrance.
No southbound entrance (use SH20B or Massey Road)
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 — Maungakiekie-Tāmaki Board Onehunga
13 Neilson Street — Onehunga Wharf, Onehunga, Penrose, Mt Wellington
Hillsborough 15 Route 12 Queenstown Road — Epsom, Royal Oak Northbound exit and southbound entrance
Auckland — Puketāpapa Board
16 Route 15 Hillsborough Road – Hillsborough, Blockhouse Bay
Mount Roskill 18 Route 4 Dominion Road – Mount Roskill
19.7 19 Maioro Street – New Lynn, Sandringham Waterview Connection begins
Auckland — Albert-Eden Board Waterview 23.8 24A SH 16 west (Northwestern Motorway) — Helensville, Wellsford SH 20 and Southwest Motorway ends
Waterview Connection ends
24B SH 16 east (Northwestern Motorway) — Auckland CBD
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

See also

References
  1. "Waterview Connection". NZTA.
  2. "SH20A improvements to airport journeys now open to traffic". NZ Transport Agency. 29 August 2017. Retrieved 3 September 2017.
  3. "Friday night transformation of intersection on SH20A to Auckland airport". NZ Transport Agency. 17 May 2018. Retrieved 20 May 2018.
  4. Dearnaley, Mathew (18 May 2009). "Another piece slots into city's commuter jigsaw". The New Zealand Herald. Retrieved 5 March 2010.
  5. "SH20-1 Manukau Extension". NZTA.
  6. "Western ring route progressing". The New Zealand Herald. 7 June 2010. Retrieved 9 July 2010.
  7. "Mangere Bridge Opened Today". The New Zealand Herald. 25 July 2010. Retrieved 1 August 2010.
  8. "Auckland's Waterview Tunnel open to traffic at last". Stuff.co.nz. 2 July 2017. Retrieved 2 July 2017.
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