The Western Ring Route is a motorway system in Auckland, New Zealand. It runs along (from south to north) the entire Southwestern Motorway (State Highway 20), most of the Northwestern Motorway (part of SH 16), the entire Upper Harbour Motorway, and the entire Upper Harbour Highway (the last two forming SH 18). When the Upper Harbour Highway is upgraded to motorway status, the route will surpass the Southern Motorway to become the longest motorway in New Zealand at 48 kilometres in length. It runs through Manukau, West Auckland, and the North Shore, bypassing the Auckland city centre and thus providing a second motorway route through the Auckland isthmus.

History

The ring route had been planned as early as the first half of the 20th century. Some critics have alleged that the rerouting of State Highway 1 over the Auckland Harbour Bridge (to ensure toll revenues) was a primary contributor to the decades-long delays. The rerouting is alleged to have significantly contributed to the need for a massive motorway through the centre of Auckland, severely damaging inner city suburbs such as Freemans Bay and Grafton. The section of SH 20 from Queenstown Road to Richardson Road (the Mount Roskill Extension) opened on 15 May 2009. The section of SH 18 connecting the Greenhithe Bridge and SH 16 (the Upper Harbour Motorway) and the extension of SH 16 to Brigham Creek Road opened in August 2011. Construction of the Waterview Connection began in late 2011 and it was opened to traffic on 2 July 2017. This completed the route as a highway, with a remaining section of SH 18 still to be upgraded to motorway standard. The opening of the Waterview Connection allows traffic to travel along the entire length of the highway, from SH 1 near Rosedale to SH 1 at Manukau. The Upper Harbour Highway section was upgraded to motorway status as part of the Northern Corridor Improvements project. Construction started in April 2018 and was completed in June 2023.

Major junctions

{| class="wikitable" ! Location ! km ! # ! Destinations ! Notes || 2.4 || 2 || Route 26 Albany Highway || Motorway begins