Editing Porirua (section)

===Road===
Wellington and Porirua are linked by the [[Johnsonville–Porirua Motorway]], part of [[State Highway 59 (New Zealand)|State Highway 59]] within Porirua and [[State Highway 1 (New Zealand)|State Highway 1]] beyond Porirua. Road improvements have progressively reduced travel times between Wellington and Porirua and increased the demand for housing development in Porirua. In 1940, the Centennial Highway developments saw the opening of a four-lane high-speed highway in [[Ngauranga Gorge]] bypassing the slower routes through Ngaio and Khandallah. During the 1950s, the high-speed [[Johnsonville–Porirua Motorway]] was built through Tawa on the eastern side of the valley. The first section from Johnsonville to the Tawa turnoff at Takapu Road at the southern entrance to Tawa opened on 15 December 1951, broadly following the line of the old North Island Main Trunk railway.<ref name="Cassells">{{cite book |author= Cassells, K. R. |title= Tawa – Enterprise and Endeavour |year=1988|publisher=Tawa Borough Council |page= 65 }}</ref> It reduced road travel times and considerably improved access between Wellington and Porirua by eliminating the need to use the narrow, winding road through the bottom of the Tawa valley in the Glenside area. The second section, from Takapu Road to Porirua, opened about 1956 and allowed through traffic to bypass the lower speed road through Tawa. The Johnsonville bypass connecting the south end of the motorway to the top of Ngauranga Gorge opened about 1958, completing the four-lane road link between Wellington and Porirua.

On 3 October 1936, a road bridge was opened across the entrance to the Pauatahanui Inlet connecting Paremata to Dolly Varden, known as Mana from 1960, eliminating a 22-kilometre journey around Pauatahanui Inlet to Plimmerton. The bridge became part of SH 1 when centennial highway developments saw the completion of a highway from Pukerua Bay to Paekākāriki. A second bridge was built in 2004 allowing two lanes of traffic in each direction.<ref name = bridges />

In the late 1960s, reclamation work began to the east of the 1960 rail reclamation from Porirua to Paremata, allowing the construction of a four-lane expressway alongside the railway. The expressway opened in the early 1970s, with room allowed for a future interchange at Whitford Brown Avenue. The reclamation work largely eliminated the north and south lagoons created by the rail reclamation on the east side of the harbour and reduced the size of the central lagoon, known as Aotea Lagoon. An intersection between SH 1 and Mungavin Avenue remained at Porirua until 1989 when the intersection was replaced with a grade-separated roundabout interchange with State Highway 1 passing under the interchange.

The [[Transmission Gully Motorway]] was constructed between 2014 and 2021, providing an eastern bypass of Porirua.  On 7 December 2021, shortly before its opening, SH 1 was shifted to the Transmission Gully Motorway and the former SH 1 route through Porirua was renumbered SH 59.<ref name="State Highway 59 switch confirmed for December">{{cite press release |url= https://www.nzta.govt.nz/media-releases/state-highway-59-switch-confirmed-for-december/ |title= State Highway 59 switch confirmed for December |publisher=New Zealand Transport Agency |date=18 November 2021 |access-date=18 November 2021}}</ref>