SH20 (New Zealand)

The SH20 is the South Western Motorway in Auckland, which is both the primary access to the Airport and also serves as a bypass for through traffic, avoiding the congested CBD area. The route also includes two spurs, more directly serving the airport. It starts at Manukau towards the southern edge of Auckland's sprawling urban area and initially heads west before turning north west as it passes through junction 3. This is a stretched diamond, formed with two half diamond junctions connected by SH20B, the first of the two spurs. The Motorway then skirts round the Mangere area to meet the second spur, SH20A. This junction gives priority to the spur from/to the north, although conversely there is no direct access from SH20A to the southbound SH20.

Northern portal of the Waterview Tunnel

Continuing north, SH20 crosses the Mangere Inlet on Mangere Bridge, briefly following the coast past Onehunga before cutting inland through some dense suburbs. Until quite recently the motorway came to an end in these suburbs, but in 2017 a new tunnel opened, cutting under the suburbs to reach SH16, Northwestern Motorway at Waterview. The junction had previously just served what is now the local route 11, but was thoroughly rebuilt to accept the new motorway, which climbs rapidly from the tunnel to cross Oakley Creek and SH16 on bridges. This has resulted in a right merge for traffic heading west on SH16 from SH20.

SH20A (George Bolt Memorial Drive, also known as the Airport Motorway) is a motorway spur which starts at junction 9 of SH20, and as noted above, it continues the mainline from the north. The motorway section of the route previously came to an end at a signalised crossroads at the first main junction, but was extended south in 2017 to meet a roundabout on the edge of the airport zone. The final section of the road in to the terminal car parks appears to be an unnumbered local road. A large industrial area extends to the west of the motorway and to the east of the more recent extension.

SH20B (Puhinui Road) is a non-motorway spur which starts at junction 3 of SH20. After connecting the two parts of this junction, effectively as CD lanes, the route turns west and cuts through what is currently open countryside. A wide inlet is crossed by bridge, with the route quickly coming to an end at the roundabout just beyond. Unnumbered local roads continue into the airport terminal area.