&sq=Qlik&lang=&file=File:State_Highway_20_NZ.svg) | ||||
|---|---|---|---|---|
| Southwestern Motorway | ||||
 | ||||
&sq=Qlik&lang=&file=File:Southwestern_Motorway_from_Mount_Roskill.jpg) The Southwestern Motorway seen from Puketāpapa / Mount Roskill in 2011 | ||||
| Route information | ||||
| Maintained by NZ Transport Agency | ||||
| Length | 25 km (16 mi) | |||
| Existed | 1977–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 | |||
| Location | ||||
| Country | New Zealand | |||
| Highway system | ||||
| ||||
&sq=Qlik&lang=&file=File:State_Highway_20a_NZ.svg){kind=small} George Bolt Memorial Drive | |
|---|---|
| Location | SH 20 at Māngere – SH 20A Airport |
| Length | 4.1 km (2.5 mi) |
&sq=Qlik&lang=&file=File:State_Highway_20b_NZ.svg){kind=small} Puhinui Road | |
|---|---|
| Location | SH 20 at Puhinui – SH 20B at Airport |
| Length | 2.3 km (1.4 mi) |
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&sq=Qlik&lang=&file=File:Southwestern_Motorway_20211023_142034.jpg)
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.