{{short description|Motorway in New Zealand}} {{Use dmy dates|date=March 2022}} {{Use New Zealand English|date=June 2015}} {{infobox road | name = Transmission Gully {{nativename|mi|Te Ara Nui o Te Rangihaeata }} | alternate_name = [[State Highway 1 (New Zealand)|State Highway 1]] | country = NZL | type = SH | route = 1 | map = {{mapframe | from = Transmission Gully motorway.map | zoom = 10 | text = Map of the Transmission Gully motorway | frame = yes | frame-width = 290 | frame-height = 260 | frame-align = center }} | map_custom = yes | length_km = 27 | direction_a = North | direction_b = South | terminus_a = {{jct|country=NZL|SH|1|SH|59|dir1=north|name1=[[Kāpiti Expressway]]|dir2=south|name2=Whareroa Road}} at [[Mackays Crossing]] | destinations = {{hlist | [[Paekākāriki]] | [[Pāuatahanui]] | [[Whitby, New Zealand|Whitby]] | [[Waitangirua]] | [[Cannons Creek, New Zealand|Cannons Creek]] | [[Kenepuru]] | [[Linden, New Zealand|Linden]] }} | junction = {{jct|country=NZL|||SH|59|name1=Paekākāriki Link Road|to2=Paekākāriki|name2=Centennial Highway}} near [[Paekākāriki]]<br />{{jct|country=NZL|SH|58|name1=Paremata-Haywards Road}} at [[Pāuatahanui]] | terminus_b = {{jct|country=NZL|SH|1|SH|59|dir1=south|name1=[[Johnsonville-Porirua Motorway]]|dir2=north|name2=Johnsonville-Porirua Motorway}} at [[Linden, New Zealand|Linden]] | established = 30 March 2022 | history = | maint = Ventia on behalf of NZ Transport Agency }} The '''Transmission Gully''' motorway ({{Langx|mi|Te Ara Nui o Te Rangihaeata}}) is a {{convert|27|km||adj=mid|-long|abbr=off}}, four-lane [[motorway]] running through [[Transmission Gully, Wellington|Transmission Gully]] north of [[Wellington]], New Zealand; it is part of [[State Highway 1 (New Zealand)|State Highway 1]].<ref name="Nzta1">{{cite web|url=http://www.nzta.govt.nz/projects/wellington-northern-corridor/transmission-gully |title=Transmission Gully motorway |work=NZ Transport Agency |accessdate=18 December 2017}}</ref> Construction began on 8 September 2014. Completion was originally scheduled for April 2020, but contractual negotiations and difficulties resulting from the [[COVID-19 pandemic]] caused delays.<ref>{{Cite news |newspaper=[[The Dominion Post (Wellington)|The Dominion Post]] |date=13 December 2021 |first=Joel |last=MacManus |title=Transmission Gully will not open in 2021, transport agency confirms |url=https://www.stuff.co.nz/dominion-post/news/wellington/127262329/transmission-gully-will-not-open-in-2021-transport-agency-confirms |via=[[Stuff (website)|Stuff]] |access-date=16 December 2021 }}</ref> The motorway was officially opened on 30 March 2022 and opened to public traffic the following day.<ref>{{cite web |title=Transmission Gully opens to traffic after the road was first proposed 100 years ago |url=https://www.nzherald.co.nz/nz/live-transmission-gully-opens-to-traffic-after-the-road-was-first-proposed-100-years-ago/7KEDS6O5RW6F5UK633LA7VPXMI/ |access-date=31 March 2022 |publisher=[[The New Zealand Herald]] |date=31 March 2022}}</ref>
==Location== Transmission Gully is a chain of steep-sided, isolated [[Valley|valleys]] running approximately north–south between the [[Kāpiti Coast]] and [[Tawa, New Zealand|Tawa]] through hills east of [[Porirua]].
An 1879 proposal for a [[Haywards–Plimmerton Line]] railway route north from Wellington envisaged using these valleys but the line was never built.<ref>{{Cite news |date=4 January 1879 |title=The Wellington-Foxton Railway Line |url=https://paperspast.natlib.govt.nz/newspapers/NZTIM18790104.2.14 |work=New Zealand Times}}</ref>
The gully's name comes from the 110,000-volt transmission line that formerly ran through it. The line, built in 1924, linked Wellington to the [[Mangahao hydroelectric station]] near [[Shannon, New Zealand|Shannon]], and later to the wider [[North Island]] transmission grid.<ref>{{Cite news |date=4 November 1924 |title=Mangahao opened |url=https://paperspast.natlib.govt.nz/newspapers/EP19241104.2.61 |work=Evening Post}}</ref><ref>{{Cite news |date=30 March 1925 |title=City Power System |url=https://paperspast.natlib.govt.nz/newspapers/DOM19250330.2.92 |work=The Dominion}}</ref>
Transmission Gully lies mostly within the boundaries of [[Porirua]], but it is sparsely populated and most of the land is farmland, forest, or scrub. There are some areas with [[Lifestyle block|lifestyle blocks]], particularly near [[Pāuatahanui]]. A property alongside the motorway, owned by economist and philanthropist [[Gareth Morgan (economist)|Gareth Morgan]] and his wife, features sculptures including a large park bench and a rainbow-coloured bridge which are visible to travellers on the motorway.<ref>{{Cite web |date=2024-01-06 |title=Gareth Morgan leaves his mark on Transmission Gully |url=https://www.rnz.co.nz/news/national/506161/gareth-morgan-leaves-his-mark-on-transmission-gully |access-date=2025-09-23 |website=RNZ |language=en-nz}}</ref><ref>{{Cite web |last=Amery |first=Mark |date=21 April 2022 |title=Transmission Gully art: Blink and you still miss it |url=https://www.stuff.co.nz/entertainment/arts/128399468/transmission-gully-art-blink-and-you-still-miss-it |access-date=2025-09-23 |website=Stuff}}</ref> Transmission Gully is also home to [[Battle Hill Farm Forest Park]].
An archaeological investigation carried out prior to construction of the motorway found evidence of pre-European Māori middens, pits, terraces and pā near the coast at Paekakariki and the Pāuatahanui Inlet. Pre-European Māori and early European settlers preferred to live near the coast, but the bulk of the motorway route is further inland and unlikely to have been permanently occupied.<ref>{{Cite book |url=https://www.epa.govt.nz/assets/FileAPI/proposal/NSP000033/Hearings/205869a2a3/BoD-Volume-5-36-Final-Report-and-Decision-of-the-BOI-into-the-Transmission-Gully-Proposal-Vol-1.pdf |title=Final Report and Decision of the Board of Inquiry into the Transmission Gully Proposal |date=June 2012 |publisher=Board of Inquiry into the Transmission Gully Proposal |isbn=978-0-478-34878-1 |location=[Wellington, New Zealand] |pages=161-164}}</ref>
==Motorway route==
[[File:Transmission Gully Motorway Pāuatahanui interchange.jpg|thumb|Transmission Gully Motorway, Pāuatahanui exit]] A highway connecting the [[Kāpiti Coast]] to [[Pāuatahanui]] through the Wainui Saddle was first proposed in 1919 by [[William Hughes Field]], the [[Member of parliament|MP]] for [[Ōtaki (New Zealand electorate)|Ōtaki]] at the time, as one of two alternatives to the steep, narrow and windy Paekakariki Hill Road between [[Paekākāriki]] and Pāuatahanui.<ref name="ep-1919">{{Cite news |title=Transport Links With Manawatu |newspaper=[[The Evening Post (New Zealand)|The Evening Post]] |date=7 June 1919 | volume=XCVII |issue=133 |page=4 |via=Papers Past, [[National Library of New Zealand]] |url= https://paperspast.natlib.govt.nz/newspapers/EP19190607.2.15?end_date=31-12-1920&items_per_page=10&query=paekakariki+road&snippet=true&start_date=01-01-1918 |access-date=29 April 2021 }}</ref> One of his proposals became the main route north of Wellington from [[Ngauranga]] to Paekākāriki through [[Pukerua Bay]], known as '''Centennial Highway'''. This route began construction in 1936 and opened on 4 November 1939,<ref name="pauatahanui-history">{{cite book |last= Reilly |first= Helen |title= Pāuatahanui: A local history |year= 2013 |publisher= Pāuatahanui Residents Association |location= Wellington |isbn= 978-0-473-25439-1 |pages= 42, 128–9 }}</ref> with the section north from Pukerua Bay running along a narrow strip of coastline below the Paekakariki escarpment.<ref name="tracks-escarpment">{{cite web|url= http://tracks.org.nz/track/show/1358 |title= Paekakariki escarpment |publisher= Tracks.org |date=14 May 2015}}</ref>
In the succeeding years public interest in alternative routes remained, and consideration was still given to constructing a route through the Wainui Saddle as Field had envisaged. A popular rumour persisted for many years that the [[United States Marine Corps|US Marines]] stationed on the Kāpiti coast during World War II made an offer to the New Zealand government to build the road, but there is no evidence of the offer having been made.<ref>{{cite news |title=End of road for 'urban myth' |newspaper=The Dominion Post |date=10 August 2013 |first=John |last=Bishop |url=http://i.stuff.co.nz/dominion-post/comment/columnists/9010925/End-of-road-for-urban-myth |access-date=13 April 2023 |via=[[Stuff (website)|Stuff]]}}</ref>
The Transmission Gully route complements the previous Centennial Highway route (now [[State Highway 59 (New Zealand)|State Highway 59]]) along the coast, and provides a new route between the [[Kāpiti Coast]] and Wellington. From its northern terminus at [[Mackays Crossing]], the route proceeds a short distance to an interchange providing access to Paekākāriki and Pukerua Bay before rising steeply inland to the Wainui Saddle, and then gently descends through [[Transmission Gully, Wellington|Transmission Gully]] following the Horokiri Stream to Pāuatahanui, where an interchange with [[State Highway 58 (New Zealand)|State Highway 58]] provides access to and from the [[Hutt Valley]]. It continues south around the eastern edge of the [[Porirua]] suburbs of [[Whitby, New Zealand|Whitby]], [[Waitangirua]] and [[Cannons Creek, New Zealand|Cannons Creek]], with an interchange providing access to local roads constructed at the same time as the motorway that link with these suburbs, before crossing the Te Ara a Toa Bridge, a {{convert|90|m||adj=mid|-high|abbr=off}} structure spanning {{convert|300|m|abbr=off}} across Cannons Creek. A subsequent interchange links to a local road, again constructed along with the motorway, that provides access to Porirua's city centre, before the motorway terminates at [[Linden, New Zealand|Linden]] on the boundary of Porirua and [[Wellington City Council|Wellington City]], where it merges on to the older [[Johnsonville–Porirua Motorway]]. The length is {{convert|27|km|abbr=off}}, with a maximum [[grade (slope)|grade]] of about 8.3 percent between the Paekākāriki Interchange and the Wainui Saddle.<ref>{{Cite news |title=Driver's guide to Transmission Gully: Time savings, fuel spots, safety checks and more |url=https://www.stuff.co.nz/dominion-post/news/wellington/128196233/drivers-guide-to-transmission-gully-time-savings-fuel-spots-safety-checks-and-more |publisher=[[Stuff (website)|Stuff]] |date=30 March 2022 |access-date=30 March 2022 }}</ref>
== Controversy == Developing a Transmission Gully road has been a topic of considerable debate in Wellington politics for some time, even as far back as 1919.<ref name="ep-1919" /><ref name="timeline" />
Supporters claimed that it would improve access to [[Wellington]] city, arguing that the existing coastal route is too congested, is accident-prone, and could be damaged in a serious earthquake. [[Peter Dunne]], former MP for Ohariu, said that "[i]mproving Wellington City's northern access and egress is a vital key to the future economic performance and prosperity of the whole region, and the Transmission Gully highway is a vital link in that chain".<ref>[http://www.unitedfuture.org.nz/press/show_item.php?t=0&i=1570 Prendergast needs to move on (United Future press release)]</ref>
Opponents of Transmission Gully stated that there were better ways to improve access to Wellington. The highway would require an extremely steep gradient on its northernmost end and many opponents considered that it would thus not actually offer any improvement over the existing coastal highway. The route that the highway would have to take is along the major fault line of the region, which would make it at least as earthquake prone as the existing coastal highway.
Some suggested that the existing coastal route should be upgraded, rather than building a completely new route. This was the original recommendation of the Regional Council, and was put forward as the primary alternative to building Transmission Gully. Public submissions to the Council were in favour of Transmission Gully, and the Council changed its stance in response.
Opponents of upgrading the coastal route said that doing so would cause significant disruption to the communities it passes through, whereas Transmission Gully avoids urban areas. The former Mayor of Porirua, [[Jenny Brash]], said that an upgrade would generate large numbers of complaints from Porirua residents, and would therefore have difficulty receiving resource consent.<ref>[http://www.pcc.govt.nz/GetImage.aspx?ImageID=3794d4c0-8d10-4047-a055-aad1cff9c459 Porirua City Council submission on Transmission Gully]</ref> Others, such as the [[Green Party of Aotearoa New Zealand|Green Party]] and the lobby group Option 3, believed that the money would be better spent on improving [[public transport in Wellington|Wellington's public transport]], particularly the existing rail line. They argued that the original choice between building Transmission Gully or upgrading the coastal route was a [[false dichotomy]], and that in reality neither option was necessary or desirable.<ref>{{cite news |last1= Ray |first1=Adam |date=22 Feb 2006 |title= Option 3 to tackle transport woes |work=Dominion Post | id={{Proquest|338208345}}}}</ref> ===Cost=== Some opponents of the Transmission Gully project believed that its overall cost was too high, and that the region had insufficient funds to spend on it. Then Mayor of Wellington, [[Kerry Prendergast]], described the project as "unaffordable".<ref>[http://www.stuff.co.nz/3999701a11.html Transmission Gully unaffordable – Wellington mayor (Dominion Post)]</ref> It was suggested that making Transmission Gully a [[toll road]] would help solve this problem, but tolls might discourage drivers from using the new route and would cover only a fraction of the funds necessary to build the highway.<ref>{{Cite web |date=2019-08-29 |title=NZTA rejects advice, making Transmission Gully free |url=https://www.rnz.co.nz/news/national/397738/nzta-rejects-advice-making-transmission-gully-free |access-date=2025-09-21 |website=RNZ |language=en-nz}}</ref><ref>{{Cite web |last=Morrison |first=Russell |date=3 July 2018 |title=The case for tolling Transmission Gully does not add up |url=https://www.stuff.co.nz/national/politics/opinion/105157030/the-case-for-tolling-transmission-gully-does-not-add-up |access-date=2025-09-21 |website=Stuff}}</ref>
In May 2012, [[Julie Anne Genter]], the Greens' spokeswoman on transport, described the motorway as incurring costs of $1 billion when the official business case benefits were $600 million, in order to ease congestion for an unlikely projected growth of 1500 vehicles per day.<ref>{{cite web |last=Genter |first=Julie Anne |date=15 May 2012 |title=Transmission Gully Figures Don't Stack Up |url=http://www.stuff.co.nz/dominion-post/news/transmission-gully/6919679/Transmission-Gully-figures-don-t-stack-up |accessdate=13 August 2012 |work=Stuff}}</ref> In February 2020 it was announced that the expected cost of $850m had been increased by another $191m.<ref>{{Cite web |date=14 February 2020 |title=Wellington's Transmission Gully project blows out by extra $191m |url=https://www.rnz.co.nz/news/national/409535/wellington-s-transmission-gully-project-blows-out-by-extra-191m |access-date=15 February 2020 |website=[[RNZ]] |language=en-nz}}</ref> In March 2021 the road was reported to cost a projected $1.25 billion by its then-expected opening date in September 2021, and would not include a planned extra merge lane at the Linden interchange to relieve congestion.<ref name="stuff-20210305">{{Cite web |last1=Te |first1=Mandy |last2=Witton |first2=Bridie |date=5 March 2021 |title=Another speed bump for Transmission Gully: Merge-lane extension at Linden on hold |url=https://www.stuff.co.nz/national/124441486/another-speed-bump-for-transmission-gully-mergelane-extension-at-linden-on-hold |access-date=29 April 2021 |work=[[Stuff (website)|Stuff]] |publisher=[[Stuff (company)|Stuff]]}}</ref>
== Construction == [[File:Transmission Gully Motorway Construction near Porirua.jpg|thumb|Construction of the motorway, east of Porirua, in December 2017]] Although first proposed in 1919, it was only late in the first decade of the 21st century that serious steps were taken towards construction. The [[Wellington Region|Greater Wellington Regional Council]], in preparing its Western Corridor Plan, initially rejected Transmission Gully as unaffordable, preferring to upgrade the existing coastal route, but changed its position after public consultation.
In 2009 [[Steven Joyce]] was Minister of Transport in the [[Fifth National Government of New Zealand|Fifth National Government]], and was lobbied by MPs [[Peter Dunne]] and [[Nathan Guy]] for Transmission Gully as part of the Levin to Airport [[Roads of National Significance|Road of National Significance]]. It had been proposed for years, but delayed as too expensive. He considered upgrading the existing road instead, but after the engineers talked of "stacking one direction of the highway on top of the other along the bottom of the cliff at Pukerua Bay, or wiping out much of Pukerua Bay village, and taking off the end of the bluff at Plimmerton", he saw Transmission Gully as the only practical option. But he was concerned about traffic reaching the northern end of the gully highway and having to stop at the Paraparaumu or Waikanae traffic lights. While a planner with foresight 50 years earlier had designated land for the Sandhills motorway from Raumati to Waikanae, the previous government had proposed allowing it to be used by the local district council for a new local road. Using the old highway route through the Paraparaumu and Waikanae shopping areas would require bulldozing houses and splitting the two towns in half. The NZTA proposed other options, such as the existing highway route, at several community meetings, but a full Sandhills Expressway on the old designation won by 2009, although opposed by [[Jenny Rowan]], the Green Party [[Mayor of Kapiti Coast]].<ref name=Joyce>{{cite book |last= Joyce |first= Steven |title= On the Record |year= 2023 |publisher=Allen & Unwin |location= Auckland |isbn= 978-1-99100-646-2 |pages= 145-149}}</ref> On 15 December 2009 Joyce announced the Government's commitment to the project as one of seven Roads of National Significance, with a predicted cost of NZ$1.025 billion.<ref name="stuff3162234">{{cite web |url=http://www.stuff.co.nz/national/3162234/Tolls-to-fund-Transmission-Gully-route |title=Tolls to fund Transmission Gully route |last=Williamson |first=Kerry|date=15 December 2009|publisher=The Dominion Post |accessdate=15 December 2009}}</ref> [[File:Transmission_Gully_Motorway_southbound_towards_Battle_Hill_Farm_Forest_Park.jpg|thumb|Looking southbound on the motorway]] On 15 August 2011, the New Zealand Transport Agency (NZTA), Porirua City Council, and [[Transpower New Zealand Limited|Transpower]] jointly applied to the [[Environmental Protection Authority (New Zealand)|Environmental Protection Authority]] (EPA) for notices of requirement and [[resource consent]]s for the Transmission Gully Proposal.<ref>{{cite web |url= http://www.epa.govt.nz/Resource-management/tg/Pages/default.aspx |title=Transmission Gully Proposal |last= |publisher = Environmental Protection Authority |date=August 2011 |accessdate=25 June 2012}}</ref> On 4 May 2012, after a series of public hearings, the EPA-appointed board of inquiry into the proposal stated in a draft decision that it would grant resource consents for it.<ref>{{cite web |url= http://www.scoop.co.nz/stories/BU1205/S00190/inquiry-board-gives-draft-approval-for-transmission-gully.htm |title=Inquiry Board gives draft approval for Transmission Gully |work=Scoop News |date= 4 May 2012 |accessdate= 4 May 2012}}</ref> On 22 June 2012, the EPA released the board of inquiry's final report.<ref>{{cite web |url= http://www.epa.govt.nz/Resource-management/tg/Pages/Final-report-and-decision.aspx |title= Final report and decision on the applications from the New Zealand Transport Agency (NZTA), Porirua City Council, and Transpower New Zealand Limited, for Notices of Requirement and Resource Consents for the Transmission Gully Proposal |author= Board of Inquiry into the Transmission Gully Proposal |publisher = Environmental Protection Authority |date= 12 June 2012 |accessdate=25 June 2012}}</ref> The board approved the resource consents and the notices of requirement needed.<ref>{{cite press release |url= http://www.scoop.co.nz/stories/AK1206/S00497/transmission-gully-proposal-approved.htm |title=Transmission Gully Proposal approved |publisher = Environmental Protection Authority |date= 22 June 2012 |accessdate=25 June 2012}}</ref><ref name=timeline>{{Cite news |title=Timeline: Transmission Gully's 103-year history |url=https://www.rnz.co.nz/news/national/464297/timeline-transmission-gully-s-103-year-history |publisher=[[Radio New Zealand|RNZ]] |date=30 March 2022 |access-date=30 March 2022 }}</ref>
On 16 May 2013, national grid owner Transpower applied for consent to the Kāpiti Coast District Council to rebuild its Valley Road, Paraparaumu, substation to 220 kV and build two short transmission lines to connect it to the two [[Bunnythorpe]] to [[Haywards]] 220 kV lines to the east. This would allow Transpower to demolish the existing 110 kV line between Pāuatahanui and Paraparaumu through Transmission Gully, rather than having to relocate it around the motorway.<ref>{{cite web |url= http://www.stuff.co.nz/dominion-post/news/local-papers/kapiti-observer/8354142/Troubled-powerlines-could-go |title= Troubled power lines could go |first= Joel |last= Maxwell |publisher= The Dominion Post (via Stuff.co.nz) |date= 26 February 2013 |accessdate= 28 July 2013}}</ref><ref>{{cite web |url= http://www.kapiticoast.govt.nz/Planning/Resource-Consents/Notified-Resource-Consents/Transpower-NZ-Ltd/ |title= Notified Resource Consents and Notices of Requirement – Transpower NZ Ltd |publisher= Kāpiti Coast District Council |accessdate= 28 July 2013}}</ref>
In spite of significant opposition, construction of the four-lane motorway began on 8 September 2014<ref>{{cite news |title=Transmission Gully work finally begins |date=8 September 2014 |url= https://www.nzherald.co.nz/business/companies/construction/transmission-gully-work-finally-begins/JWX6DFNZERFHDJJ6NC2RTSDC34/ |agency=APNZ |newspaper=[[The New Zealand Herald]] |access-date=25 April 2025}}</ref><ref name=timeline /> with completion originally scheduled for April 2020.<ref>{{cite news |title=Transmission Gully motorway construction 'considerably behind' schedule |newspaper=The Dominion Post |first=Joel |last=Maxwell |date=29 November 2019 |url= https://www.stuff.co.nz/motoring/117777481/transmission-gully-motorway-construction-considerably-behind-schedule |access-date=1 January 2023 |via=[[Stuff (website)|Stuff]] }}</ref> Delays due to contractual disputes and difficulties caused by the COVID-19 pandemic pushed the budget out and the opening was scheduled for late 2021.<ref name="nzta-sep2021-delayed">{{Cite web |author= |date=18 September 2021 |title=Transmission Gully opening date delayed by Covid-19 |url= https://www.nzta.govt.nz/projects/wellington-northern-corridor/transmission-gully-motorway/about-the-project/project-news/waka-kotahi-nz-transport-agency-is-working-with-the-transmission-gully-public-private-partnership-contractor-wellington-gateway-partnership-wgp-and-its-subcontractor-cpb-heb-joint-venture-to-confirm-a-new-opening-date-for-the-motorway-new-news-page/ |access-date=21 September 2021 |work=Waka Kotahi NZ Transport Agency}}</ref> Transmission Gully was formally declared a motorway on 16 August 2021 with the declaration coming into force 28 days later.<ref>{{cite news |date=23 August 2021 |title= Government Roading Powers (Declaration of Motorway in Kāpiti Coast District, Upper Hutt City, Porirua City and Wellington City) Order 2021 |url= https://gazette.govt.nz/notice/id/2021-ln3593 |work=[[New Zealand Gazette|Te Kāhiti o Aotearoa / New Zealand Gazette]] |location=Wellington |access-date=19 September 2021}}</ref> It opened in 2022, as did the Pekapeka to Otaki expressway. The Otaki to Levin expressway was cancelled and then rescheduled by the [[Sixth Labour Government of New Zealand|Sixth Labour Government]], and has not restarted.<ref name=Joyce />
===Opening===
On 30 March 2022, [[Prime Minister of New Zealand|Prime Minister]] [[Jacinda Ardern]] officially opened the motorway.<ref name=timeline /><ref name="TG opening">{{Cite web |date=30 March 2022 |title=Wellingtonians 'so excited' to try out Transmission Gully |url=https://www.stuff.co.nz/dominion-post/300553447/wellingtonians-so-excited-to-try-out-transmission-gully |access-date=30 March 2022 |website=[[Stuff (website)|Stuff]] |language=en}}</ref> The road was officially gifted the name ''Te Ara Nui o Te Rangihaeata / Great Path of Te Rangihaeata'' by the Ngati Toa tribe in honour of Te Rangihaeata, a chief who played a leading role in the [[Wairau Affray]] and the [[Hutt Valley Campaign]] in the [[New Zealand Wars]].<ref>{{Cite web |date=29 March 2022 |title=Te Ara Nui o Te Rangihaeata |url=https://streetnames.nz/new-zealand/te-ara-nui-o-te-rangihaeata/ |access-date=30 March 2022 |website=NZ Street Names |language=en-NZ}}</ref> The motorway passes to the side of the location of the [[Battle of Battle Hill]], where the final stand-off between [[Te Rangihaeata]] and forces loyal to the [[British Empire]] took place before Te Rangihaeata retreated to [[Poroutawhao]] in the [[Horowhenua District]].<ref>{{Cite encyclopedia |first=Wattie |last=Carkeek |editor-first=A. H. |editor-last=McLintock |editor-link=Alexander Hare McLintock |encyclopedia=[[An Encyclopaedia of New Zealand]] |date=1966 |title=Te Rangihaeata |url=https://teara.govt.nz/en/1966/te-rangihaeata |via=Te Ara – the Encyclopedia of New Zealand |access-date=30 March 2022}}</ref>
The motorway opened to motorists on the morning of 31 March 2022. On opening day, a [[Holden Commodore (VF)|Holden VF Commodore]] police car drove into the northbound [[Runaway truck ramp|truck arrester bed]] due to driver error. It was repaired and continued in service until it reached the end of its service life in May that year. After being retired the car was preserved at the [[Southward Car Museum]].<ref>{{Cite web |last=Green |first=Kate |date=2022-03-31 |title=Police accidentally drive into runaway vehicle pit on Transmission Gully – and prove it works |url=https://www.stuff.co.nz/dominion-post/wellington/300554942/police-accidentally-drive-into-runaway-vehicle-pit-on-transmission-gully--and-prove-it-works |access-date=2022-09-21 |website=[[Stuff (website)|Stuff]] |language=en}}</ref><ref>{{Cite web |last=Haxton |first=David |date=20 July 2022 |title=History of four iconic police Holden Commodores preserved |url=https://www.nzherald.co.nz/kapiti-news/news/history-of-four-iconic-police-holden-commodores-preserved/EAVAAEJSPFXVFCMXGUWVWSRB7I/ |access-date=2022-09-21 |website=[[The New Zealand Herald]] |language=en-NZ}}</ref>
=== Further developments === In February 2026 Transmission Gully's speed limit will change from {{Convert|100|km/h|abbr=on}} to {{Convert|110|km/h|abbr=on}}.<ref>{{Cite news |date=15 February 2026 |title=Transmission Gully speed limit signs fast-tracked due to weather |url=https://www.1news.co.nz/2026/02/14/transmission-gully-speed-limit-change-fast-tracked-due-to-weather/ |access-date=15 February 2026 |work=1News}}</ref>
== Environmental issues == The route passes near the [[Pāuatahanui Inlet]], an environmentally sensitive wetland area. Construction of the motorway has been identified as the likely cause of increased sedimentation in the inlet.<ref>{{Cite web|url=https://www.rnz.co.nz/news/national/397724/roading-project-likely-suffocating-wildlife-in-porirua-harbour-survey|title=Roading project likely suffocating wildlife in Porirua Harbour – Survey|date=29 August 2019|website=[[RNZ]] |language=en-nz|access-date=21 December 2019}}</ref>
In October 2023 it was reported that pests such as possums, stoats, and ferrets were using Transmission Gully as a route to kiwi populations. After the highway was completed, the number of ferrets found in traps increased. In some cases, half of kiwi populations had been killed within weeks.<ref>{{Cite web |date=13 October 2023 |title=Ferret highway: Transmission Gully creates path for pests to move south |url=https://www.nzherald.co.nz/nz/ferret-highway-transmission-gully-creates-path-for-pests-to-move-south/YC4MFEYW2BBOPIPA6KTRURL5HE/ |access-date=2023-10-30 |website=[[The New Zealand Herald]] |language=en-NZ}}</ref>
== Benefits == A report commissioned by Infrastructure New Zealand in 2025 showed that in 2024 Transmission Gully saved northbound travellers an average of nine minutes per journey, compared to the old route in 2019. Travel times on both the old route and Transmission Gully are shorter and more reliable throughout the day, ranging from a median five minutes across the whole day to 31 minutes in peak traffic on the busiest days. Faster travel times are offset by higher vehicle operating costs due to the hillier route and higher speed limit. Between 2022 and 2024, no deaths were recorded on Transmission Gully and the rate of serious injury was lower than that on the old route during the same period.<ref name=":0">{{Cite book |last=Brunsdon |first=Nick |url=https://infrastructure.org.nz/wp-content/uploads/2025/09/INZ-Transmission-Gully-Report_DIGITAL_Final_16.09.25.pdf |title=Analysis of Economic and Social Benefits of Transmission Gully and Kāpiti Expressway [report] |last2=Stroombergen |first2=Adolf |date=September 2025 |publisher=Infrastructure New Zealand}}</ref>
The Transmission Gully motorway means that 74,000 (15%) more people now live within 60 minutes' drive of Porirua's central business district. The population of Porirua has grown and house prices have risen due to increased accessibility.<ref name=":0" />
==Name in official records== Land information New Zealand (LINZ) has applied the name gifted by Ngāti Toa Rangatira to the NZ Topo 50 map BP31.<ref>{{cite web|url=https://www.linz.govt.nz/products-services/maps/new-zealand-topographic-maps/topo50-map-chooser/topo50-map-bp31-porirua |title=Topo 50 map bp31 Porirua – 1 06|access-date=24 December 2022 }}</ref> Neither of the names ''Te Ara Nui o Rangihaeata'' or ''Transmission Gully'' appear in the New Zealand Gazetteer.
==Interchanges== {{Jcttop |unit=km |unnum=yes |state_col=[[Territorial authority]] |nocty=yes}} {{Jctint |county_special=[[Kāpiti Coast District]] |cspan=2 |location_special=Mackays Crossing |km=0 |road={{jct|country=NZL|SH|59|name1=Whareroa Road}} – [[Queen Elizabeth Park, Kāpiti Coast|Queen Elizabeth Park]] |notes=Northern terminus, {{jct|country=NZL|SH|1}} continues north as [[Kāpiti Expressway]] }} {{Jctint |location_special=Paekākāriki |type=incomplete |km=2 |road={{jct|country=NZL|||SH|59|name1=Paekākāriki Link Road|to2=Paekākāriki|name2=Centennial Highway}} – [[Paekākāriki]], [[Plimmerton]] |notes=Southbound entrance and northbound exit }} {{jctbridge |county_special=[[Kāpiti Coast District]] /<br />[[Porirua City]] /<br />[[Upper Hutt City]] tripoint |location_special=Wainui |km=5 |place=''Pouāwhā / Wainui Saddle {{convert|253|m|abbr=on}}'' }} {{Jctint |county_special=[[Porirua City]] |cspan=4 |location_special=Pāuatahanui |km=17 |road={{jct|country=NZL|SH|58|name1=Paremata-Haywards Road}} – [[Hutt Valley]], [[Pāuatahanui]] }} {{Jctint |location_special=Waitangirua |km=19 |road=Waitangirua Link Road – [[Waitangirua]], [[Whitby, New Zealand|Whitby]] |notes= }} {{jctbridge |location_special=Cannons Creek |rspan=1 |km=23 |bridge=''Te Ara a Toa Bridge (Cannons Creek)'' |bspan= }} {{Jctint |location_special=Kenepuru |type=incomplete |km=26 |road=Kenepuru Link Road – [[Porirua]], [[Tawa, New Zealand|Tawa]] |notes=Southbound exit only, both northbound and southbound entrance }} {{Jctint |county_special=[[Wellington City]] |location_special=Linden |type=incomplete |km=27 |road={{jct|country=NZL|SH|59|dir1=north|name1=[[Johnsonville-Porirua Motorway]]}} - [[Porirua]]<br />{{jct|country=NZL|SH|1|dir1=south|name1=[[Johnsonville-Porirua Motorway]]}} - [[Johnsonville, New Zealand|Johnsonville]], [[Wellington]] |notes=Exit from northbound Johnsonville-Porirua Motorway and entry to southbound Johnsonville-Porirua Motorway only<br />Southern terminus, {{jct|country=NZL|SH|1}} continues south as [[Johnsonville-Porirua Motorway]] }} {{Jctbtm|conv=no|keys=incomplete}}
==See also== *[[List of motorways and expressways in New Zealand]]
==References== {{reflist|2}}
==External links== {{Commons}} * [https://www.nzta.govt.nz/projects/wellington-northern-corridor/transmission-gully-motorway Transmission Gully motorway], NZTA * [https://web.archive.org/web/20070927043444/http://www.gw.govt.nz/story_images/3787_AdoptedWesternCo_s7591.pdf Wellington Regional Council's adopted Western Corridor Plan] (PDF) * [https://web.archive.org/web/20070205082203/http://www.option3.org.nz/ Option 3, a pressure group opposed to the Transmission Gully Motorway]
{{New Zealand motorway list}}
[[Category:Motorways in New Zealand]] [[Category:Transport in Wellington]] [[Category:Porirua]]