:Thornlie–Cockburn line

Initial plans for the Mandurah line had the line as a spur off the Armadale line along the Kwinana freight railway in the same manner as the present-day Thornlie line. The South West Metropolitan Railway Master Plan was released in March 1999, detailing the route and stations along the railway. The South West Metropolitan Railway would have diverged from the Armadale line at Kenwick, entering a tunnel to pass under the Perth-bound Armadale line track, Albany Highway, Roe Highway, and the freight railway. It would have then travelled parallel and on the southern side of the freight railway, with stations in Thornlie near Spencer Road, Nicholson Road, and in Canning Vale near Ranford Road, and provisions for a future station at Karel Avenue to serve Jandakot Airport. The railway would have then entered another tunnel at Jandakot, known as the Glen Iris tunnel, to go into the median of the Kwinana Freeway, continuing south from there to Mandurah. Several level crossings on the freight railway were planned to be replaced by road-over-rail bridges, at Albany Highway, Spencer Road, Nicholson Road, and Karel Avenue.{{cite web |title=South West Metropolitan Railway Master Plan |url=http://www.newmetrorail.wa.gov.au/NMR/Documents/Plans/Master%20Plan/SWMR%20MP%20-%20199903%20-%20Complete.zip |website=New MetroRail |archive-url=https://web.archive.org/web/20070828214331/http://www.newmetrorail.wa.gov.au/NMR/Documents/Plans/Master%20Plan/SWMR%20MP%20-%20199903%20-%20Complete.zip |archive-date=28 August 2007 |pages=40, 43, 45 |date=March 1999}}

File:Armadale Line viewed from pedestrian crossing near Beckenham Station, Western Australia, October 2023 08.jpg

As part of an extension of Roe Highway from Welshpool Road to Kenwick Link and realignment of Albany Highway in the late 1990s and early 2000s, the first stage of the Kenwick tunnel was built and Albany Highway was grade separated from the freight railway.{{cite press release |first1=Murray |last1=Criddle |first2=Richard |last2=Court |title=Inspection today of the $30.3 million Kenwick Joint Project construction site |url=https://www.wa.gov.au/government/media-statements/Court-Coalition-Government/Inspection-today-of-the-$30.3-million-Kenwick-Joint-Project-construction-site-19990913 |publisher=Government of Western Australia |access-date=18 July 2023 |date=13 September 1999 |archive-date=18 July 2023 |archive-url=https://web.archive.org/web/20230718072943/https://www.wa.gov.au/government/media-statements/Court-Coalition-Government/Inspection-today-of-the-$30.3-million-Kenwick-Joint-Project-construction-site-19990913 |url-status=live }} The {{convert|200|m|ft|adj=mid|-long}} Glen Iris tunnel was also constructed as part of an extension of the Kwinana Freeway in 2000.{{cite web |title=Past project creates the Thornlie-Cockburn Link |url=https://www.metronet.wa.gov.au/news/latest-news/past-project-creates-the-thornlie-cockburn-link |website=Metronet |access-date=18 July 2023 |date=15 March 2021 |archive-date=18 July 2023 |archive-url=https://web.archive.org/web/20230718072942/https://www.metronet.wa.gov.au/news/latest-news/past-project-creates-the-thornlie-cockburn-link |url-status=live }}{{cite web |last1=Duboudin |first1=Tony |title=Unused 21-year-old tunnel to be upgraded for Perth rail line |url=https://www.railjournal.com/regions/australia-nz/unused-21-year-old-tunnel-to-be-upgraded-for-perth-rail-line/ |website=International Railway Journal |access-date=18 July 2023 |date=10 April 2021 |archive-date=18 July 2023 |archive-url=https://web.archive.org/web/20230718072940/https://www.railjournal.com/regions/australia-nz/unused-21-year-old-tunnel-to-be-upgraded-for-perth-rail-line/ |url-status=live }}

Following the election of the Labor Party in 2001, the Mandurah line was rerouted to follow a more direct route along the Kwinana Freeway to the Perth central business district. It was decided to build the Thornlie line as a one station branch of the Armadale line to Spencer Road using the Kenwick tunnel.{{cite news |last1=Robb |first1=Trevor |title=Rail Switch – New train link across city foreshore |work=The West Australian |date=17 July 2001 |page=1}}{{cite news |last1=Robb |first1=Trevor |last2=Capp |first2=Geraldine |title=Rail link row cools down |work=The West Australian |date=18 July 2001 |page=4}} Building Nicholson Road station was also considered.{{cite news |last1=Robb |first1=Trevor |title=The radical rail plan |work=The West Australian |date=21 July 2001 |page=9}}{{cite news |last1=Robb |first1=Trevor |title=Job fear in rail move |work=The West Australian |date=1 July 2002 |page=25}} A new master plan was released in 2002.{{cite news |last1=Robb |first1=Trevor |title=ALP claims win on freeway line |work=The West Australian |date=14 August 2002 |page=4}} Spencer Road was planned to be grade separated and Thornlie station was planned to have a bus interchange and parking for about 450 cars. Patronage for Thornlie station was projected to be 3,500 boardings per day. Patronage was not forecast to be high enough for Nicholson Road station to be built initially, but it was expected to be built in the future. Train frequencies were planned to be four trains per hour upon opening in December 2004.{{cite web |title=Perth Urban Rail Development Project – Supplementary Master Plan |url=http://www.newmetrorail.wa.gov.au/NMR/Documents/Plans/Master%20Plan/PURD%20MP%20-%20200208%20-%20Supplementary.pdf |website=New MetroRail |archive-url=https://web.archive.org/web/20070829024413/http://www.newmetrorail.wa.gov.au/NMR/Documents/Plans/Master%20Plan/PURD%20MP%20-%20200208%20-%20Supplementary.pdf |archive-date=29 August 2007 |date=August 2002 |page=66–67, 70, 77, 92, 114 |isbn=0-7307-2426-3}}

File:Kwinana freight railway viewed from Albany Highway bridge 02.jpg viewed from the Albany Highway bridge|alt=Long shot of a dual track freight railway to the left of a tunnel portal]]

New MetroRail was formed in 2003 as a division of the Public Transport Authority to manage extensions to railways in Perth, including the Mandurah line, the Thornlie line, and an extension of the Joondalup line to Clarkson station.{{cite news |last1=Manton |first1=Cian |title=Railway expansion on track |work=The West Australian |date=21 March 2003 |page=11}} The second stage contract for the Kenwick tunnel was awarded to John Holland Group in March 2003 at a cost of A$14.225{{nbsp}}million. The second stage consisted of {{convert|380|m}} of tunnel; the realignment of {{convert|1.4|km}} of the Kwinana freight railway, which was leased by Australian Railroad Group at the time; and the construction of noise walls. The total tunnel length after the two stages was {{convert|440|m}}.{{cite press release |first1=Alannah |last1=MacTiernan |title=Go-ahead for completion of Kenwick Rail Tunnel |url=https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Go-ahead-for-completion-of-Kenwick-Rail-Tunnel-20030514 |publisher=Government of Western Australia |access-date=18 July 2023 |date=14 May 2003 |archive-date=18 July 2023 |archive-url=https://web.archive.org/web/20230718072942/https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Go-ahead-for-completion-of-Kenwick-Rail-Tunnel-20030514 |url-status=live }}{{cite web |title=Kenwick Tunnel – Stage 2 |url=http://www.newmetrorail.wa.gov.au/Default.aspx?tabid=97 |website=New MetroRail |archive-url=https://web.archive.org/web/20070828234659/http://www.newmetrorail.wa.gov.au/Default.aspx?tabid=97 |archive-date=28 August 2007}} Workers on the John Holland site went on strike in May 2003 to campaign for better pay and conditions.{{cite news |last1=Taylor |first1=Robert |title=French method seduces union men |work=The West Australian |date=28 May 2003 |page=2}} Construction was also disrupted by a solidarity strike in January 2005 in relation to pay conditions for workers on the Mandurah line.{{cite news |last1=MacDonald |first1=Kim |title=Union strikes for better rail deal |work=The West Australian |date=6 January 2005 |page=3}}{{cite news |last1=MacDonald |first1=Kim |title=Respite in rail pay claim strike |work=The West Australian |date=11 January 2005 |page=12}}

A new traction substation at Beckenham was constructed to power the Thornlie line and provide backup power to the Armadale line, which was mainly powered by a substation at East Perth. The contract for that was awarded to Western Power Corporation in September 2003 at a cost of $3.3{{nbsp}}million.{{cite press release |first1=Alannah |last1=MacTiernan |title=Public Transport Authority signs electricity feeder station contract |url=https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Public-Transport-Authority-signs-electricity-feeder-station-contract-20030917 |publisher=Government of Western Australia |access-date=18 July 2023 |date=17 September 2003 |archive-date=18 July 2023 |archive-url=https://web.archive.org/web/20230718072944/https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Public-Transport-Authority-signs-electricity-feeder-station-contract-20030917 |url-status=live }}{{cite web |title=Thornlie Spur Line – Beckenham Sub Station |url=http://www.newmetrorail.wa.gov.au/Default.aspx?tabid=98 |website=New MetroRail |archive-url=https://web.archive.org/web/20060217082534/http://www.newmetrorail.wa.gov.au/Default.aspx?tabid=98 |archive-date=17 February 2006}} Other work involved relocating BP's Kewdale White Oil Line,{{cite web |title=OnTrack: Issue 4 |url=http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202003-12.pdf |website=New MetroRail |archive-url=https://web.archive.org/web/20070828235427/http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202003-12.pdf |archive-date=28 August 2007 |page=8 |date=December 2003}} which is a pipeline that carries jet fuel, diesel and petrol from the Kwinana import terminal to Kewdale via the freight railway.{{rp|775}}

An invitation to tender was sent out on 25 June 2003 for the main contract to build the Thornlie line. This involved constructing Thornlie station, {{convert|2.9|km}} of single track railway, a rail bridge across the Canning River and a road bridge for Spencer Road across the Thornlie line and freight railway. The tender was planned to close on 28 August 2003,{{cite press release |first1=Alannah |last1=MacTiernan |title=Tenders advertised for multi-million dollar Thornlie rail works |url=https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Tenders-advertised-for-multi-million-dollar-Thornlie-rail-works-20030625 |publisher=Government of Western Australia |access-date=18 July 2023 |date=25 June 2003 |archive-date=18 July 2023 |archive-url=https://web.archive.org/web/20230718072944/https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Tenders-advertised-for-multi-million-dollar-Thornlie-rail-works-20030625 |url-status=live }} but that was extended to 16 December 2003. Barclay Mowlem was announced as the preferred tenderer in February 2004 and was awarded the contract by April 2004. The estimated value of the contract was $30{{nbsp}}million. By then, the planned opening date was February 2005.{{cite press release |first1=Alannah |last1=MacTiernan |title=Preferred tenderer announced for Thornlie station |url=https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Preferred-tenderer-announced-for-Thornlie-station-20040212 |publisher=Government of Western Australia |access-date=18 July 2023 |date=12 February 2004 |archive-date=18 July 2023 |archive-url=https://web.archive.org/web/20230718072942/https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Preferred-tenderer-announced-for-Thornlie-station-20040212 |url-status=live }}{{cite web |title=OnTrack: Issue 5 |url=http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202004-04.pdf |website=New MetroRail |archive-url=https://web.archive.org/web/20070829000131/http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202004-04.pdf |archive-date=29 August 2007 |page=5 |date=April 2004}} Construction had begun by July 2004.{{cite web |title=OnTrack: Issue 6 |url=http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202004-07.pdf |website=New MetroRail |archive-url=https://web.archive.org/web/20070829000009/http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202004-07.pdf |archive-date=29 August 2007 |page=4 |date=July 2004}} Construction was disrupted by strikes. The Construction, Forestry, Mining and Energy Union and union officials were initially fined for breaching an enterprise bargaining agreement, but the fines were overturned by the Federal Court in June 2007.{{cite news |title=Union, officials fined |work=The West Australian |date=30 April 2005 |page=51}}{{cite news |last1=MacDonald |first1=Kim |title=Rail strike list found in smoko shed |work=The West Australian |date=18 March 2006 |page=40}}{{cite news |last1=MacDonald |first1=Kim |title=Union hails court victory against 'witch-hunt' by building watchdog |work=The West Australian |date=9 June 2007 |page=4}} Thornlie station and the Thornlie line were officially opened on 7 August 2005 by Premier Geoff Gallop, Minister for Planning and Infrastructure Alannah MacTiernan, and member for Kenwick Sheila McHale.{{cite press release |first1=Alannah |last1=MacTiernan |first2=Geoff |last2=Gallop |title=Thornlie line and station opening a major milestone for public transport network |url=https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Thornlie-line-and-station-opening-a-major-milestone-for-public-transport-network-20050807 |publisher=Government of Western Australia |access-date=18 July 2023 |date=7 August 2005 |archive-date=10 July 2023 |archive-url=https://web.archive.org/web/20230710094613/https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/Thornlie-line-and-station-opening-a-major-milestone-for-public-transport-network-20050807 |url-status=live }}{{cite web |title=OnTrack: Issue 10 |url=http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202005-10.pdf |website=New MetroRail |archive-url=https://web.archive.org/web/20070828235301/http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202005-10.pdf |archive-date=28 August 2007 |page=8}} Full service began on 8 August 2005.{{cite web |title=OnTrack: Issue 9 |url=http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202005-07.pdf |website=New MetroRail |archive-url=https://web.archive.org/web/20070828235906/http://www.newmetrorail.wa.gov.au/NMR/Documents/Resources/Publications/On%20Track/OnTrack%202005-07.pdf |archive-date=28 August 2007 |pages=1, 3 |date=July 2005}}

An extension of the Thornlie line to link up with the Mandurah line had been proposed several times in the 2010s. In December 2012, the Labor Party announced it planned to incorporate the Thornlie line into a loop line to link the proposed Airport line to the Fremantle line via the Armadale and Mandurah lines if it were to win the 2013 state election. This was part of its proposed Metronet plan. There would have been stations at Nicholson Road, Ranford Road and a station called South Lake at the intersection with the Mandurah line.{{cite web |last1=Preston |first1=Robyn |title=Labor promises new Perth rail network |url=https://www.watoday.com.au/national/western-australia/labor-promises-new-perth-rail-network-20121216-2bhhh.html |website=WAtoday |access-date=19 July 2023 |date=16 December 2012 |archive-date=23 April 2021 |archive-url=https://web.archive.org/web/20210423164117/https://www.watoday.com.au/national/western-australia/labor-promises-new-perth-rail-network-20121216-2bhhh.html |url-status=live }}{{cite web |last1=Zaw |first1=Yolanda |title=Labor unveils $1.6b rail plans |url=https://thewest.com.au/news/wa/labor-unveils-16b-rail-plans-ng-ya-341803 |website=The West Australian |access-date=19 July 2023 |date=16 December 2012 |archive-date=3 July 2023 |archive-url=https://web.archive.org/web/20230703164242/https://thewest.com.au/news/wa/labor-unveils-16b-rail-plans-ng-ya-341803 |url-status=live }} The Liberal Party won the election, so that plan did not go ahead.{{cite web |title=How the West was won: Landslide for Liberals |url=https://www.abc.net.au/news/2013-03-09/wa-election-2013-live-coverage/4563048 |website=ABC News |access-date=3 March 2024 |date=9 March 2013 |archive-date=2 October 2023 |archive-url=https://web.archive.org/web/20231002015858/https://www.abc.net.au/news/2013-03-09/wa-election-2013-live-coverage/4563048 |url-status=live }} In 2015, RAC WA called for the Thornlie line to be extended to Cockburn Central station on the Mandurah line.{{cite web |last1=Curro |first1=Francis |title=Make tracks on extension |url=https://www.perthnow.com.au/community-news/comment-news/make-tracks-on-extension-c-921366 |website=PerthNow |agency=Comment News |access-date=4 October 2023 |date=14 July 2015 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023116/https://www.perthnow.com.au/community-news/comment-news/make-tracks-on-extension-c-921366 |url-status=live }} The Liberal government's 2016 Transport @ 3.5 million plan called for the extension to be built by the time that Perth reaches a population of 2.7{{nbsp}}million.{{cite web |last1=Mckenzie |first1=Matt |title=Nalder gets digging in transport plan |url=https://www.businessnews.com.au/article/Nalder-gets-digging-in-transport-plan |website=Business News |access-date=19 July 2023 |date=29 July 2016 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091114/https://www.businessnews.com.au/article/Nalder-gets-digging-in-transport-plan |url-status=live }}{{cite web |title=Transport @ 3.5 million |url=https://www.vincent.wa.gov.au/agenda/2016/20161018/briefingagenda/att/ptp1.pdf |website=City of Vincent |access-date=19 July 2023 |pages=15, 17–18, 48 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091116/https://www.vincent.wa.gov.au/agenda/2016/20161018/briefingagenda/att/ptp1.pdf |url-status=live }}

Ahead of the 2017 state election, both major parties committed to extending the Thornlie line to Cockburn Central station. The Liberal government said it could be done at a cost of $520{{nbsp}}million and be open in late 2023,{{cite web |last1=Acott |first1=Kent |title=New $520m rail link between Thornlie and Cockburn |url=https://thewest.com.au/news/perth/new-520m-rail-link-between-thornlie-and-cockburn-ng-b88364289z |website=The West Australian |access-date=19 July 2023 |date=25 January 2017 |archive-date=13 December 2021 |archive-url=https://web.archive.org/web/20211213040732/https://thewest.com.au/news/perth/new-520m-rail-link-between-thornlie-and-cockburn-ng-b88364289z |url-status=live }}{{cite web |last1=Weber |first1=David |title=Thornlie to Cockburn rail line announcement last-minute attempt to win seats: WA Labor |url=https://www.abc.net.au/news/2017-01-25/wa-thornlie-cockburn-rail-line-announced-by-barnett-government/8210902 |website=ABC News |access-date=19 July 2023 |date=25 January 2017 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091105/https://www.abc.net.au/news/2017-01-25/wa-thornlie-cockburn-rail-line-announced-by-barnett-government/8210902 |url-status=live }}{{cite web |last1=Young |first1=Emma |title=Government promises Thornlie rail extension through Canning Vale |url=https://www.watoday.com.au/national/western-australia/government-promises-thornlie-rail-extension-through-canning-vale-20170125-gtymmw.html |website=WAtoday |access-date=19 July 2023 |date=25 January 2017 |archive-date=2 January 2022 |archive-url=https://web.archive.org/web/20220102033119/https://www.watoday.com.au/national/western-australia/government-promises-thornlie-rail-extension-through-canning-vale-20170125-gtymmw.html |url-status=live }} whereas Labor said it could be constructed for $474{{nbsp}}million by 2021 as part of its revised Metronet plans.{{cite web |last1=O'Connor |first1=Andrew |title=WA Election: $2.5bn cost of Metronet will not increase net debt, says Labor |url=https://www.abc.net.au/news/2017-02-06/wa-election-labor-unveils-metronet-costings/8245362 |website=ABC News |access-date=19 July 2023 |date=6 February 2017 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091113/https://www.abc.net.au/news/2017-02-06/wa-election-labor-unveils-metronet-costings/8245362 |url-status=live }}{{cite web |last1=Acott |first1=Kent |title=Parties need to bring public along for the ride |url=https://thewest.com.au/politics/state-election-2017/parties-need-to-bring-public-along-for-the-ride-ng-b88359700z |website=The West Australian |access-date=19 July 2023 |date=9 February 2017 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091105/https://thewest.com.au/politics/state-election-2017/parties-need-to-bring-public-along-for-the-ride-ng-b88359700z |url-status=live }} Labor won the 2017 election and planning for the Thornlie–Cockburn Link began in late March 2017.{{cite web |last1=Smith |first1=Ben |title=State Govt starts planning for Thornlie train line extension |url=https://www.perthnow.com.au/community-news/comment-news/state-govt-starts-planning-for-thornlie-train-line-extension-c-806515 |website=PerthNow |access-date=19 July 2023 |date=6 April 2017 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091109/https://www.perthnow.com.au/community-news/comment-news/state-govt-starts-planning-for-thornlie-train-line-extension-c-806515 |url-status=live }} In May, following negotiations between the federal and state governments, it was announced that federal funding for the cancelled Perth Freight Link would be used on the Thornlie–Cockburn Link, subject to assessment by Infrastructure Australia.{{cite web |last1=Spagnolo |first1=Joe |title=$2.3 billion jobs boost for WA |url=https://www.perthnow.com.au/news/wa/23-billion-jobs-boost-for-wa-ng-b53b044c6aa3848a4c809169a1ea7645 |website=PerthNow |access-date=4 October 2023 |date=7 May 2017 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023114/https://www.perthnow.com.au/news/wa/23-billion-jobs-boost-for-wa-ng-b53b044c6aa3848a4c809169a1ea7645 |url-status=live }} The September 2017 state budget gave the Thornlie–Cockburn Link a cost of $535.8{{nbsp}}million.{{cite press release |first1=Mark |last1=McGowan |first2=Rita |last2=Saffioti |first3=Ben |last3=Wyatt |title=METRONET well underway with major funding injection |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/METRONET-well-underway-with-major-funding-injection-20170907 |publisher=Government of Western Australia |access-date=27 September 2023 |date=7 September 2017 |archive-date=27 September 2023 |archive-url=https://web.archive.org/web/20230927013502/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/METRONET-well-underway-with-major-funding-injection-20170907 |url-status=live }}{{cite web |title=Western Australia budget backs rail growth |url=https://www.railwaygazette.com/western-australia-budget-backs-rail-growth/45155.article |website=Railway Gazette International |access-date=4 October 2023 |date=13 September 2017 |archive-date=7 February 2023 |archive-url=https://web.archive.org/web/20230207092441/https://www.railwaygazette.com/western-australia-budget-backs-rail-growth/45155.article |url-status=live }}

The business case for the Thornlie–Cockburn Link was submitted to Infrastructure Australia in August 2017.{{cite web |title=First step in bid for Infrastructure Australia funding |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/first-step-in-bid-for-infrastructure-australia-funding |website=Metronet |access-date=19 July 2023 |date=21 August 2017 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091107/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/first-step-in-bid-for-infrastructure-australia-funding |url-status=live }} In November 2018, Infrastructure Australia released its assessment of the project, adding the project to the Infrastructure Priority List as a "Priority Project" and giving it a projected economic benefit of $969{{nbsp}}million and a benefit–cost ratio of 1.2. Other options considered were only extending the Thornlie line to Nicholson Road and having a station there, or only extending the line to Ranford Road and having stations at Ranford Road and Nicholson Road. Extending the line the whole way to Cockburn was found to be the best choice. Infrastructure Australia recommended that the contract for the Thornlie–Cockburn Link be combined with the contract for the Yanchep Rail Extension of the Joondalup line to save costs during procurement,{{cite web |title=Project Evaluation Summary METRONET: Thornlie–Cockburn Link |url=https://www.infrastructureaustralia.gov.au/sites/default/files/2019-06/Project-Evaluation-Summary-METRONET-TCL_1.pdf |website=Infrastructure Australia |access-date=19 July 2023 |date=1 November 2018 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091114/https://www.infrastructureaustralia.gov.au/sites/default/files/2019-06/Project-Evaluation-Summary-METRONET-TCL_1.pdf |url-status=live }}{{cite web |last1=Loneragan |first1=David |title=Two Metronet projects granted priority status by Infrastructure Australia |url=https://www.railexpress.com.au/two-metronet-projects-granted-priority-status-by-infrastructure-australia/ |website=Rail Express |access-date=19 July 2023 |date=16 November 2018 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091114/https://www.railexpress.com.au/two-metronet-projects-granted-priority-status-by-infrastructure-australia/ |url-status=live }}{{cite web |last1=Wright |first1=Shane |title=National infrastructure tsar gives green light to Perth Metronet plan |url=https://thewest.com.au/business/infrastructure/national-infrastructure-tsar-gives-green-light-to-perth-metronet-plan-ng-b881022272z |website=The West Australian |access-date=19 July 2023 |date=16 November 2018 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164526/https://thewest.com.au/business/infrastructure/national-infrastructure-tsar-gives-green-light-to-perth-metronet-plan-ng-b881022272z |url-status=live }} although local contractors expressed concerns that the two projects had different requirements, were in different parts of Perth, and that combining the projects would price out smaller contractors.{{cite web |last1=Mckenzie |first1=Matt |title=Contractors call for rethink on procurement |url=https://www.businessnews.com.au/article/Contractors-call-for-rethink-on-procurement |website=Business News |access-date=27 January 2025 |date=26 February 2018 |url-access=subscription}} The Infrastructure Australia assessment allowed $700{{nbsp}}million in federal funding to be spent on the Thornlie–Cockburn Link and the Yanchep Rail Extension, of which $350{{nbsp}}million was for the Thornlie–Cockburn Link.{{cite web |title=Federal Funding Secured |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/federal-funding-secured |website=Metronet |access-date=10 September 2023 |date=15 November 2018 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023123/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/federal-funding-secured |url-status=live }}{{cite web |last1=Jarvis |first1=Lucy |title=Yanchep: Infrastructure Australia approves $700m federal contribution to Metronet rail projects |url=https://www.perthnow.com.au/community-news/north-coast-times/yanchep-infrastructure-australia-approves-700m-federal-contribution-to-metronet-rail-projects-c-868113 |website=PerthNow |access-date=10 September 2023 |date=16 November 2018 |agency=North Coast Times |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023114/https://www.perthnow.com.au/community-news/north-coast-times/yanchep-infrastructure-australia-approves-700m-federal-contribution-to-metronet-rail-projects-c-868113 |url-status=live }}

Enabling legislation was introduced to the Parliament of Western Australia in May 2018{{cite web |title=METRONET Bill read into Parliament today |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/metronet-bill-read-into-parliament-today |website=Metronet |access-date=10 September 2023 |date=10 May 2018 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023120/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/metronet-bill-read-into-parliament-today |url-status=live }}{{cite web |title=Metronet legislation to pave way for construction of Yanchep rail extension |url=https://www.perthnow.com.au/community-news/north-coast-times/metronet-legislation-to-pave-way-for-construction-of-yanchep-rail-extension-c-851748 |website=PerthNow |access-date=10 September 2023 |date=1 June 2018 |agency=North Coast Times |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023115/https://www.perthnow.com.au/community-news/north-coast-times/metronet-legislation-to-pave-way-for-construction-of-yanchep-rail-extension-c-851748 |url-status=live }} and passed in November 2018.{{cite web |title=METRONET Rail Enabling Bill Passed |url=https://www.metronet.wa.gov.au/news/latest-news/metronet-rail-enabling-bill-passed |website=Metronet |access-date=10 September 2023 |date=16 November 2018 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023118/https://www.metronet.wa.gov.au/news/latest-news/metronet-rail-enabling-bill-passed |url-status=live }}

The project definition plan, detailing the scope of the project, for the Thornlie–Cockburn Link was approved by state cabinet in July 2018.{{cite web |title=Two projects move to next phase |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/two-projects-move-to-next-phase |website=Metronet |access-date=10 September 2023 |date=2 July 2018 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023119/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/two-projects-move-to-next-phase |url-status=live }}{{cite press release |first1=Mark |last1=McGowan |first2=Rita |last2=Saffioti |title=Two METRONET projects on track to begin construction next year |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Two-METRONET-projects-on-track-to-begin-construction-next-year-20180703 |publisher=Government of Western Australia |access-date=19 July 2023 |date=3 July 2018 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164527/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Two-METRONET-projects-on-track-to-begin-construction-next-year-20180703 |url-status=live }} The project was to involve the construction of two new stations: Nicholson Road and Ranford Road stations, each with two {{convert|150|m|adj=on}} long island platforms, full disabled access, a bus interchange for feeder buses and a park and ride. Nicholson Road station was forecast to have 2,350 boardings per day in 2031 and Ranford Road station was forecast to have 1,985 boardings per day in 2031. {{convert|14.5|km}} of new dual-track railway was to be constructed between Thornlie and Cockburn Central, using the pre-existing Glen Iris tunnel to enter the median of the Kwinana Freeway. Most of this track was to be along the southern side of the freight railway, with the final {{convert|3|km}} within the median of the Kwinana Freeway between the two Mandurah line tracks. {{convert|3|km}} of single track railway between Beckenham junction and Thornlie station was to be duplicated, including constructing a new bridge across the Canning River. The Kenwick tunnel was already designed for a double tracked railway. To make way for the Thornlie line, {{convert|11|km}} of the freight railway was to be relocated slightly north.{{cite web |title=Thornlie–Cockburn Link Project Definition Plan |url=https://www.metronet.wa.gov.au/Portals/31/Project%20Documents/Thornlie-Cockburn%20Link/Thornlie-Cockburn%20Link%20PDP%20Summary_WEB.PDF |website=Metronet |access-date=18 July 2023 |archive-date=11 June 2023 |archive-url=https://web.archive.org/web/20230611134859/https://www.metronet.wa.gov.au/Portals/31/Project%20Documents/Thornlie-Cockburn%20Link/Thornlie-Cockburn%20Link%20PDP%20Summary_WEB.PDF |url-status=live |date=June 2018}}{{rp|12}}

Thornlie station was to have its platform's length extended to {{convert|150|m}} and be converted to allow for through trains, including the construction of an overpass. Cockburn Central station was to have a new platform extending north from the existing Mandurah line platforms for Thornlie line trains to terminate. A new footbridge at Elliot Place was to replace the existing pedestrian level crossing there.{{rp|12}} Perth Stadium station was to have its Thornlie-bound platforms extended and additional train stowage capacity at Perth Stadium was planned to be built, allowing for direct special event services to Mandurah via Thornlie.{{rp|27}}{{cite web |title=Stadium Station Fact Sheet |url=https://www.metronet.wa.gov.au/Portals/31/Project%20Documents/Thornlie-Cockburn%20Link/Stadium%20Station%20Fact%20Sheet.pdf |website=Metronet |access-date=4 October 2023 |archive-date=11 June 2023 |archive-url=https://web.archive.org/web/20230611134941/https://www.metronet.wa.gov.au/Portals/31/Project%20Documents/Thornlie-Cockburn%20Link/Stadium%20Station%20Fact%20Sheet.pdf |url-status=live }} At this stage, construction was planned to begin in late 2019 and finish in 2021.{{rp|6}}

A request for proposal was released in September 2018 for the design and construct contract for the Thornlie–Cockburn Link and the Yanchep Rail Extension.{{cite press release |first1=Rita |last1=Saffioti |title=Joint media statement – Wanted: Contractor to build Perth's new METRONET rail lines |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---Wanted%3A-Contractor-to-build-Perth%27s-new-METRONET-rail-lines-20180909 |publisher=Government of Western Australia |access-date=19 July 2023 |date=9 September 2018 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164528/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---Wanted%3A-Contractor-to-build-Perth%27s-new-METRONET-rail-lines-20180909 |url-status=live }}{{cite web |last1=Gameng |first1=Monica |title=Request for Proposal released for two major METRONET projects WA |url=https://www.felix.net/project-news/request-for-proposal-released-for-two-major-metronet-projects-wa |website=Felix Vendor Marketplace |access-date=19 July 2023 |date=10 September 2018 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164528/https://www.felix.net/project-news/request-for-proposal-released-for-two-major-metronet-projects-wa |url-status=live }} Two consortia were shortlisted in April 2019: METROconnex, a joint venture between Coleman Rail, Clough Group, and Georgiou Group; and NEWest Alliance, a joint venture between CPB Contractors and Downer.{{cite web |last1=Milne |first1=Peter |title=METROconnex, NEWest Alliance consortiums vie for $1.1b Metronet's Thornlie-Cockburn and Yanchep rail work |url=https://thewest.com.au/business/infrastructure/metroconnex-newest-alliance-consortiums-vie-for-11b-metronets-thornlie-cockburn-and-yanchep-rail-work-ng-b881159566z |website=The West Australian |access-date=19 July 2023 |date=6 April 2019 |archive-date=6 April 2019 |archive-url=https://web.archive.org/web/20190406130031/https://thewest.com.au/business/infrastructure/metroconnex-newest-alliance-consortiums-vie-for-11b-metronets-thornlie-cockburn-and-yanchep-rail-work-ng-b881159566z |url-status=live }}{{cite web |last1=Beyer |first1=Mark |title=Two bidders for rail projects |url=https://www.businessnews.com.au/article/Two-bidders-for-rail-projects |website=Business News |access-date=19 July 2023 |date=8 April 2019 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164538/https://www.businessnews.com.au/article/Two-bidders-for-rail-projects |url-status=live }}{{cite press release |first1=Rita |last1=Saffioti |title=METRONET's Thornlie-Cockburn Link and Yanchep Rail Extension tender reaches next phase |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/METRONET%27s-Thornlie-Cockburn-Link-and-Yanchep-Rail-Extension-tender-reaches-next-phase-20190406 |publisher=Government of Western Australia |access-date=19 July 2023 |date=6 April 2019 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164526/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/METRONET%27s-Thornlie-Cockburn-Link-and-Yanchep-Rail-Extension-tender-reaches-next-phase-20190406 |url-status=live }} In November 2019, NEWest Alliance was announced as the preferred proponent to design and build the Thornlie–Cockburn Link and the Yanchep Rail Extension.{{cite web |last1=Zimmerman |first1=Josh |title=NEWest Alliance appointed to deliver Yanchep rail extension and Thornlie-Cockburn link |url=https://thewest.com.au/business/infrastructure/newest-alliance-appointed-to-deliver-yanchep-rail-extension-and-thornlie-cockburn-link-ng-b881391617z |website=The West Australian |access-date=19 July 2023 |date=24 November 2019 |url-access=subscription |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091107/https://thewest.com.au/business/infrastructure/newest-alliance-appointed-to-deliver-yanchep-rail-extension-and-thornlie-cockburn-link-ng-b881391617z |url-status=live }}{{cite web |title=NEWest Alliance chosen for Yanchep Rail Extension |url=https://www.railway-technology.com/news/newest-alliance-yanchep-rail-extension/ |website=Railway Technology |access-date=19 July 2023 |date=26 November 2019 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091113/https://www.railway-technology.com/news/newest-alliance-yanchep-rail-extension/ |url-status=live }} The following month, the contract was signed. The value of the whole contract was $1.25{{nbsp}}billion and the value of the Thornlie–Cockburn Link portion was $716{{nbsp}}million, an increase on the $474{{nbsp}}million originally promised by Labor. $366{{nbsp}}million was to be funded by the state government and $350{{nbsp}}million funded by the federal government. The completion date was delayed by two years to 2023. The delay was blamed on negotiations with BP for relocating the Kewdale White Oil Line and with Arc Infrastructure, the new leaseholder of the Kwinana freight railway.{{cite web |last1=Gubana |first1=Benjamin |title=Metronet Thornlie-Cockburn link between Armadale and Mandurah train lines delayed to 2023 after $200m blowout |url=https://www.abc.net.au/news/2019-12-17/metronet-thornlie-cockburn-line-delayed-after-budget-blowout/11807852 |website=ABC News |access-date=19 July 2023 |date=17 December 2019 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091114/https://www.abc.net.au/news/2019-12-17/metronet-thornlie-cockburn-line-delayed-after-budget-blowout/11807852 |url-status=live }}{{cite web |last1=Smith |first1=Ben |title=Major Metronet project over budget and delayed |url=https://www.perthnow.com.au/community-news/cockburn-gazette/major-metronet-project-over-budget-and-delayed-c-896243 |website=PerthNow |agency=Cockburn Gazette |access-date=19 July 2023 |date=18 December 2019 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719091105/https://www.perthnow.com.au/community-news/cockburn-gazette/major-metronet-project-over-budget-and-delayed-c-896243 |url-status=live }}{{cite web |title=WA Government signs contracts with NEWest Alliance |url=https://www.railway-technology.com/news/wa-government-newest-alliance/ |website=Railway Technology |access-date=19 July 2023 |date=17 December 2019 |archive-date=14 May 2023 |archive-url=https://web.archive.org/web/20230514063922/https://www.railway-technology.com/news/wa-government-newest-alliance/ |url-status=live }}

The Thornlie–Cockburn Link received state environmental approval from the Environmental Protection Authority in August 2019{{cite web |title=METRONET Thornlie-Cockburn Link recommended for environmental approval |url=https://www.epa.wa.gov.au/media-statements/metronet-thornlie-cockburn-link-recommended-environmental-approval |website=Environmental Protection Authority |access-date=19 July 2023 |date=12 August 2019 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164527/https://www.epa.wa.gov.au/media-statements/metronet-thornlie-cockburn-link-recommended-environmental-approval |url-status=live }}{{cite web |last1=Rauso |first1=Adrian |title=EPA green lights $536m rail extension |url=https://www.businessnews.com.au/article/EPA-green-lights-536m-rail-extension-0 |website=Business News |access-date=27 January 2025 |date=12 August 2019 |url-access=subscription}} and federal environmental approval from the Department of the Environment and Energy in early 2020.{{cite press release |first1=Rita |last1=Saffioti |title=Thornlie-Cockburn Link gets environmental green light |url=https://www.wa.gov.au/government/media-statements/McGowan%20Labor%20Government/Thornlie-Cockburn-Link-gets-environmental-green-light-20200203 |publisher=Government of Western Australia |access-date=27 January 2025 |date=3 February 2020}}{{cite web |title=Thornlie-Cockburn Link receives federal environmental approval |url=https://www.railway-technology.com/news/thornlie-cockburn-environmental-approval/ |website=Railway Technology |access-date=19 July 2023 |date=3 February 2020 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719170028/https://www.railway-technology.com/news/thornlie-cockburn-environmental-approval/ |url-status=live }} The main environmental concerns were the impact on wetlands, bushland, and black cockatoo habitats, although most of the bushland that was planned to be cleared was degraded.{{cite web |last1=Mckenzie |first1=Matt |title=Cockatoos, wetlands on rail route |url=https://www.businessnews.com.au/article/Cockatoos-wetlands-on-rail-route |website=Business News |access-date=27 January 2025 |date=8 August 2019 |url-access=subscription}}

File:Nicholson Rd Gnangarra 061017-11.jpg bridge under construction in October 2017|alt=A level crossing with a bridge being built next to it]]

To make way for the Thornlie–Cockburn Link, the Karel Avenue and Ranford Road bridges were replaced with longer and wider bridges. The Nicholson Road bridge, which was constructed between December 2016 and May 2018 to replace a level crossing, did not have to be rebuilt as it was designed with the Thornlie–Cockburn Link in mind.{{cite web |title=Nicholson Road (Bridge) Over Rail |url=https://www.mainroads.wa.gov.au/BuildingRoads/Projects/UrbanProjects/Pages/nicholson.aspx |website=Main Roads Western Australia |archive-url=https://web.archive.org/web/20170412104834/https://www.mainroads.wa.gov.au/BuildingRoads/Projects/UrbanProjects/Pages/nicholson.aspx |archive-date=12 April 2017}}{{cite web |title=Nicholson Road (Bridge) Over Rail |url=https://project.mainroads.wa.gov.au/home/completed/Pages/nicholsonroad.aspx |website=Main Roads Western Australia |archive-url=https://web.archive.org/web/20190305020018/https://project.mainroads.wa.gov.au/home/completed/Pages/nicholsonroad.aspx |archive-date=5 March 2019}}{{cite web |last1=Acott |first1=Kent |title=$27m safety fix for rail crossing |url=https://thewest.com.au/news/australia/27m-safety-fix-for-rail-crossing-ng-ya-118646 |website=The West Australian |access-date=7 September 2023 |date=20 September 2016 |archive-date=7 September 2023 |archive-url=https://web.archive.org/web/20230907084824/https://thewest.com.au/news/australia/27m-safety-fix-for-rail-crossing-ng-ya-118646 |url-status=live }} The Karel Avenue bridge was originally constructed in 2005 and 2006 to replace a level crossing as part of the extension of Roe Highway from South Street to the Kwinana Freeway.{{cite press release |first1=Alannah |last1=MacTiernan |title=New Karel Avenue extension will improve safety and access |url=https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/New-Karel-Avenue-extension-will-improve-safety-and-access-20051130 |publisher=Government of Western Australia |access-date=7 September 2023 |date=30 November 2005 |archive-date=7 September 2023 |archive-url=https://web.archive.org/web/20230907084826/https://www.wa.gov.au/government/media-statements/Gallop-Labor-Government/New-Karel-Avenue-extension-will-improve-safety-and-access-20051130 |url-status=live }}{{cite press release |first1=Tony |last1=McRae |title=New Karel Avenue bridge will improve safety and access. |url=https://www.wa.gov.au/government/media-statements/Carpenter-Labor-Government/New-Karel-Avenue-bridge-will-improve-safety-and-access.-20060601 |publisher=Government of Western Australia |access-date=7 September 2023 |date=1 June 2006 |archive-date=7 September 2023 |archive-url=https://web.archive.org/web/20230907084824/https://www.wa.gov.au/government/media-statements/Carpenter-Labor-Government/New-Karel-Avenue-bridge-will-improve-safety-and-access.-20060601 |url-status=live }} The bridge's span was not long enough to fit the Thornlie–Cockburn Link though, so it was replaced with a longer and wider bridge between August 2019 and July 2021.{{cite web |title=Karel Avenue Upgrade |url=https://www.mainroads.wa.gov.au/projects-initiatives/all-projects/metropolitan/Karel-Avenue-Upgrade/ |website=Main Roads Western Australia |access-date=7 September 2023 |archive-date=7 September 2023 |archive-url=https://web.archive.org/web/20230907084823/https://www.mainroads.wa.gov.au/projects-initiatives/all-projects/metropolitan/Karel-Avenue-Upgrade/ |url-status=live }}{{cite press release |first1=Rita |last1=Saffioti |title=Joint media statement – Congestion busting the Karel Avenue bottleneck |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---Congestion-busting-the-Karel-Avenue-bottleneck-20190808 |publisher=Government of Western Australia |access-date=7 September 2023 |date=8 August 2019 |archive-date=7 September 2023 |archive-url=https://web.archive.org/web/20230907084825/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---Congestion-busting-the-Karel-Avenue-bottleneck-20190808 |url-status=live }}{{cite web |last1=Budihardjo |first1=Nadia |title=Traffic bottleneck area receives upgrade |url=https://www.perthnow.com.au/community-news/cockburn-gazette/traffic-bottleneck-area-receives-upgrade-c-888351 |website=PerthNow |access-date=7 September 2023 |date=8 August 2019 |agency=Cockburn Gazette |archive-date=7 September 2023 |archive-url=https://web.archive.org/web/20230907084824/https://www.perthnow.com.au/community-news/cockburn-gazette/traffic-bottleneck-area-receives-upgrade-c-888351 |url-status=live }}

The original Ranford Road bridge opened in 1985 and the second bridge was built alongside the first between 1997 and 1998, widening Ranford Road to two lanes in each direction. The second bridge was designed with the Mandurah line in mind,{{cite press release |first1=Eric |last1=Charlton |title=Contract for duplicating Ranford Road Bridge over railway at Canning Bridge |url=https://www.wa.gov.au/government/media-statements/Court-Coalition-Government/Contract-for-duplicating-Ranford-Road-Bridge-over-railway-at-Canning-Bridge-19971126 |publisher=Government of Western Australia |access-date=10 September 2023 |date=26 November 1997 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023114/https://www.wa.gov.au/government/media-statements/Court-Coalition-Government/Contract-for-duplicating-Ranford-Road-Bridge-over-railway-at-Canning-Bridge-19971126 |url-status=live }}{{cite press release |first1=Murray |last1=Criddle |title=New traffic bridge over railway line in Canning Vale eases congestion |url=https://www.wa.gov.au/government/media-statements/Court-Coalition-Government/New-traffic-bridge-over-railway-line-in-Canning-Vale-eases-congestion-19980923 |publisher=Government of Western Australia |access-date=10 September 2023 |date=23 September 1998 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023120/https://www.wa.gov.au/government/media-statements/Court-Coalition-Government/New-traffic-bridge-over-railway-line-in-Canning-Vale-eases-congestion-19980923 |url-status=live }} but nonetheless, both Ranford Road bridges are being replaced for the Thornlie–Cockburn Link so that Ranford Road can be widened to three lanes in each direction plus bus lanes and a shared path. Construction on the new bridge started in late 2020.{{cite press release |first1=Mark |last1=McGowan |first2=Rita |last2=Saffioti |title=Joint media statement – Ranford Road Station piling on Thornlie-Cockburn Link milestones |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---Ranford-Road-Station-piling-on-Thornlie-Cockburn-Link-milestones-20201204 |publisher=Government of Western Australia |access-date=10 September 2023 |date=4 December 2020 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023118/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---Ranford-Road-Station-piling-on-Thornlie-Cockburn-Link-milestones-20201204 |url-status=live }}{{cite web |title=Thornlie-Cockburn Link piles through 2020 |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/thornlie-cockburn-link-piles-through-2020 |website=Metronet |access-date=10 September 2023 |date=4 December 2020 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023120/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/thornlie-cockburn-link-piles-through-2020 |url-status=live }} The first stage of the new bridge, which consisted of seven beams, opened to traffic in November 2021,{{cite press release |first1=Rita |last1=Saffioti |title=Traffic switches to new Ranford Road Bridge |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Traffic-switches-to-new-Ranford-Road-Bridge-20211116 |publisher=Government of Western Australia |access-date=10 September 2023 |date=16 November 2021 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023116/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Traffic-switches-to-new-Ranford-Road-Bridge-20211116 |url-status=live }}{{cite web |title=Traffic flowing across new Ranford Road Bridge |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/traffic-flowing-across-new-ranford-road-bridge |website=Metronet |access-date=10 September 2023 |date=16 November 2021 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023117/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/traffic-flowing-across-new-ranford-road-bridge |url-status=live }} after which the two previous bridges were demolished. The remaining three beams of the new bridge were in place by July 2022. The bridge was meant to be completed in 2023,{{cite press release |first1=Rita |last1=Saffioti |title=Final beams installed on Ranford Road Bridge |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Final-beams-installed-on-Ranford-Road-Bridge-20220727 |publisher=Government of Western Australia |access-date=10 September 2023 |date=27 July 2022 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023119/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Final-beams-installed-on-Ranford-Road-Bridge-20220727 |url-status=live }}{{cite web |title=Tee-riffic bridge beam installation complete for Thornlie-Cockburn Link |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/tee-riffic-bridge-beam-installation-complete-for-thornlie-cockburn-link |website=Metronet |access-date=10 September 2023 |date=27 July 2022 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023116/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/tee-riffic-bridge-beam-installation-complete-for-thornlie-cockburn-link |url-status=live }} but it eventually opened in May 2024.{{cite press release |first1=Rita |last1=Saffioti |title=Joint media statement – Green light for traffic on Ranford Road Bridge |url=https://www.wa.gov.au/government/media-statements/Cook-Labor-Government/Joint-media-statement---Green-light-for-traffic-on-Ranford-Road-Bridge-20240527 |publisher=Government of Western Australia |access-date=27 May 2024 |date=27 May 2024 |archive-date=27 May 2024 |archive-url=https://web.archive.org/web/20240527031707/https://www.wa.gov.au/government/media-statements/Cook-Labor-Government/Joint-media-statement---Green-light-for-traffic-on-Ranford-Road-Bridge-20240527 |url-status=live }}{{cite web |title=Metronet milestone |url=https://www.watoday.com.au/national/metronet-milestone-20240528-p5jh7c.html |website=WAtoday |access-date=30 May 2024 |date=28 May 2024 |archive-date=29 May 2024 |archive-url=https://web.archive.org/web/20240529032940/https://www.watoday.com.au/national/metronet-milestone-20240528-p5jh7c.html |url-status=live }}

File:Construction work at the Cockburn Central railway station, December 2022 02.jpg platform extension in December 2022|alt=Train station platform with construction barriers on the platform and machinery on tracks]]

File:Thornlie Station, Western Australia, September 2023 08.jpg in September 2023|alt=Sandy construction site next to railway tracks]]

Early works for the Thornlie–Cockburn Link within the Kwinana Freeway were undertaken under a pre-existing project to widen the Kwinana Freeway throughout 2019 and 2020. This involved drainage works and the erection of barriers between the freeway and railway.{{cite press release |first1=Rita |last1=Saffioti |title=METRONET works to be integrated with Kwinana Freeway upgrade project |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/METRONET-works-to-be-integrated-with-Kwinana-Freeway-upgrade-project-20191217 |publisher=Government of Western Australia |access-date=3 October 2023 |date=17 December 2019 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023117/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/METRONET-works-to-be-integrated-with-Kwinana-Freeway-upgrade-project-20191217 |url-status=live }}{{cite web |title=WA Government's Thornlie-Cockburn Metronet rail link blows out by $200m and two years |url=https://thewest.com.au/news/transport/wa-governments-thornlie-cockburn-metronet-rail-link-blows-out-by-200m-and-two-years-ng-b881414388z |website=The West Australian |access-date=3 October 2023 |date=17 December 2019 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023114/https://thewest.com.au/news/transport/wa-governments-thornlie-cockburn-metronet-rail-link-blows-out-by-200m-and-two-years-ng-b881414388z |url-status=live }} Thornlie–Cockburn Link construction was underway by the middle of 2020.{{cite press release |first1=Mark |last1=McGowan |first2=Rita |last2=Saffioti |title=Joint media statement – First look at Thornlie-Cockburn Link's Ranford Road Station site |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---First-look-at-Thornlie-Cockburn-Link%27s-Ranford-Road-Station-site-20200823 |publisher=Government of Western Australia |access-date=27 September 2023 |date=23 August 2020 |archive-date=27 September 2023 |archive-url=https://web.archive.org/web/20230927013447/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---First-look-at-Thornlie-Cockburn-Link%27s-Ranford-Road-Station-site-20200823 |url-status=live }}

The September 2021 state budget revealed that the opening of the Thornlie–Cockburn Link would be delayed by a year to late 2024 due to a skills shortage and to ease pressure on Western Australia's construction industry.{{cite press release |first1=Mark |last1=McGowan |title=Projects adjusted to deliver a strong economy for the long term |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Projects-adjusted-to-deliver-a-strong-economy-for-the-long-term-20210909 |publisher=Government of Western Australia |access-date=19 July 2023 |date=9 September 2021 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164530/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Projects-adjusted-to-deliver-a-strong-economy-for-the-long-term-20210909 |url-status=live }}{{cite web |last1=de Kruijff |first1=Peter |title=State projects delayed to ease pressure on 'hot' WA construction market |url=https://www.watoday.com.au/national/western-australia/state-projects-delayed-to-ease-pressure-on-hot-wa-construction-market-20210909-p58qbr.html |website=WAtoday |access-date=19 July 2023 |date=9 September 2021 |archive-date=9 September 2021 |archive-url=https://web.archive.org/web/20210909064111/https://www.watoday.com.au/national/western-australia/state-projects-delayed-to-ease-pressure-on-hot-wa-construction-market-20210909-p58qbr.html |url-status=live }}{{cite web |last1=Clarke |first1=Jenna |title=Metronet projects, including Thornlie-Cockburn link and Yanchep train line, will be DELAYED by 12-months |url=https://www.perthnow.com.au/politics/state-politics/metronet-projects-including-thornlie-cockburn-link-and-yanchep-train-line-will-be-delayed-by-12-months-ng-b881999781z |website=PerthNow |access-date=19 July 2023 |date=9 September 2021 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164526/https://www.perthnow.com.au/politics/state-politics/metronet-projects-including-thornlie-cockburn-link-and-yanchep-train-line-will-be-delayed-by-12-months-ng-b881999781z |url-status=live }} The May 2022 state budget revealed that the Thornlie–Cockburn Link's cost had increased by $164.1{{nbsp}}million,{{cite web |last1=de Kruijff |first1=Peter |title=Record $33.9b for infrastructure projects as Premier plays down construction costs |url=https://www.watoday.com.au/national/record-33-9b-for-infrastructure-projects-as-premier-plays-down-construction-costs-20220511-p5akik.html |website=WAtoday |access-date=4 October 2023 |date=12 May 2022 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023116/https://www.watoday.com.au/national/record-33-9b-for-infrastructure-projects-as-premier-plays-down-construction-costs-20220511-p5akik.html |url-status=live }} a $243.8{{nbsp}}million cost increase was revealed in the May 2023 state budget,{{cite web |last1=Zimmerman |first1=Josh |title=Budget Estimates: Premier Mark McGowan refuses to rule out more blowouts to Metronet costs |url=https://thewest.com.au/news/wa/budget-estimates-premier-mark-mcgowan-refuses-to-rule-out-more-blowouts-to-metronet-costs-c-10742891 |website=The West Australian |access-date=4 October 2023 |date=23 May 2023 |url-access=subscription |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023114/https://thewest.com.au/news/wa/budget-estimates-premier-mark-mcgowan-refuses-to-rule-out-more-blowouts-to-metronet-costs-c-10742891 |url-status=live }}{{cite web |title=2023–24 Budget: Economic and Fiscal Outlook |url=https://www.parliament.wa.gov.au/WebCMS/webcms.nsf/resources/file-2023-budget-economic-outlook/$file/Economic%20and%20Fiscal%20Outlook.pdf |website=Parliament of Western Australia |access-date=4 October 2023 |page=186 |date=May 2023 |issn=1448-2630 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023117/https://www.parliament.wa.gov.au/WebCMS/webcms.nsf/resources/file-2023-budget-economic-outlook/$file/Economic%20and%20Fiscal%20Outlook.pdf |url-status=live }} and a $228{{nbsp}}million cost increase was revealed in the May 2024 state budget,{{cite web |last1=Zimmerman |first1=Josh |title=WA State Budget 2024: Treasurer Rita Saffioti announces WA’s sixth surplus in a row, Metronet blowout |url=https://thewest.com.au/politics/budget/wa-state-budget-2024-treasurer-rita-saffioti-announces-was-sixth-surplus-in-a-row-metronet-blowout-c-14593757 |website=The West Australian |access-date=9 May 2024 |date=9 May 2024 |url-access=subscription |archive-date=9 May 2024 |archive-url=https://web.archive.org/web/20240509061407/https://thewest.com.au/politics/budget/wa-state-budget-2024-treasurer-rita-saffioti-announces-was-sixth-surplus-in-a-row-metronet-blowout-c-14593757 |url-status=live }}{{cite web |first1=Andrea |last1=Mayes |first2=Keane |last2=Bourke |title=WA Budget 2024: Winners and losers from Rita Saffioti's first effort as treasurer |url=https://www.abc.net.au/news/2024-05-09/wa-budget-2024-winners-and-losers/103821950 |website=ABC News |access-date=9 May 2024 |date=9 May 2024 |archive-date=9 May 2024 |archive-url=https://web.archive.org/web/20240509061454/https://www.abc.net.au/news/2024-05-09/wa-budget-2024-winners-and-losers/103821950 |url-status=live }} taking the total cost to $1.352{{nbsp}}billion.{{cite web |title=2024–25 Budget Statements. Budget Paper No. 2 – Volume 2 |url=https://www.ourstatebudget.wa.gov.au/2024-25/budget-papers/bp2/2024-25-wa-state-budget-bp2-vol2.pdf |website=Our Budget |access-date=9 May 2024 |page=619 |archive-date=9 May 2024 |archive-url=https://web.archive.org/web/20240509062940/https://www.ourstatebudget.wa.gov.au/2024-25/budget-papers/bp2/2024-25-wa-state-budget-bp2-vol2.pdf |url-status=live }}

From 26 December 2021 to 14 January 2022, the Mandurah line was shut down between Elizabeth Quay station and Aubin Grove station to facilitate works on the Thornlie–Cockburn Link. This was the longest planned shutdown of a railway line in Perth's history at the time and was done to relocate the Mandurah line tracks between Cockburn Central station and the Glen Iris tunnel to make way for the Thornlie line tracks.{{cite web |last1=Fiore |first1=Briana |title=Mandurah train line shutdown: Everything you need to know about replacement buses and delays |url=https://thewest.com.au/politics/state-politics/mandurah-train-line-shutdown-everything-you-need-to-know-about-replacement-buses-and-delays-c-5061620 |website=The West Australian |access-date=19 July 2023 |date=23 December 2021 |url-access=subscription |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164526/https://thewest.com.au/politics/state-politics/mandurah-train-line-shutdown-everything-you-need-to-know-about-replacement-buses-and-delays-c-5061620 |url-status=live }}{{cite web |title=Mandurah Line Shutdown Fact Sheet |url=https://www.metronet.wa.gov.au/Portals/31/Mandurah%20Line%20Shutdown%20Fact%20Sheet.pdf |website=Metronet |access-date=19 July 2023 |date=November 2021 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164527/https://www.metronet.wa.gov.au/Portals/31/Mandurah%20Line%20Shutdown%20Fact%20Sheet.pdf |url-status=live }} The same section of the Mandurah line was shut down again from 26 December 2022 to 3 January 2023, with the exception of New Year's Eve. Work undertaken during that period included the installation of turnouts linking the Thornlie line with the Mandurah line, communication and signalling equipment, overhead line equipment, and {{convert|4|km}} of rail.{{cite press release |first1=Rita |last1=Saffioti |title=Mandurah Line partial shutdown for essential works |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Mandurah-Line-partial-shutdown-for-essential-works-20221101 |publisher=Government of Western Australia |access-date=3 October 2023 |date=1 November 2022 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023118/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Mandurah-Line-partial-shutdown-for-essential-works-20221101 |url-status=live }}{{cite web |title=Shutdown scores a touchdown |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/shutdown-scores-a-touchdown |website=Metronet |access-date=3 October 2023 |date=6 March 2023 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023115/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/shutdown-scores-a-touchdown |url-status=live }}

Relocating the Kewdale White Oil Line involved {{convert|11|km|0}} of horizontal drilling and about {{convert|1|km|1}} of open-trench digging.{{cite web |title=Thornlie-Cockburn Link: Beyond connecting the dots |url=https://roadsonline.com.au/thornlie-cockburn-link-beyond-connecting-the-dots/ |website=Roads & Infrastructure Magazine |publisher=Prime Creative Media |access-date=3 October 2023 |date=7 December 2021 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023116/https://roadsonline.com.au/thornlie-cockburn-link-beyond-connecting-the-dots/ |url-status=live }} An open trench pipeline was originally considered during planning, but the desire to limit disruption to the freight railway meant that predominantly horizontal directional drilling was the final option chosen.{{cite conference |last1=Aizezi |first1=Jiang |chapter=BP KWOL Pipeline Relocation – Largest Brownfield Trenchless Relocation in Australia |conference=Australasian Tunnelling Conference |edition=18th |title=ATC 2023: Australasian Tunnelling Conference: Conference Proceedings: Trends and Transitions in Tunnelling |date=5–8 November 2023 |pages=774–788 |publisher=Engineers Australia |isbn=978-1-925627-74-9 |chapter-url=https://search.informit.org/doi/epdf/10.3316/informit.T2024030600019301470148101 |access-date=30 May 2024 |archive-date=30 May 2024 |archive-url=https://web.archive.org/web/20240530080321/https://search.informit.org/doi/abs/10.3316/informit.T2024030600019301470148101 |url-status=live }}{{rp|776–777}} Drilling was complete by November 2022, after which a bridge across the Canning River for the pipeline was built.{{cite web |title=In bridges we truss |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/in-bridges-we-truss |website=Metronet |access-date=3 October 2023 |date=28 November 2022 |archive-date=5 October 2023 |archive-url=https://web.archive.org/web/20231005023116/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/in-bridges-we-truss |url-status=live }} The pipeline was shut down between 23 February and 28 February 2023 for the cutover.{{rp|787–788}}

In February 2022, it was announced that the Armadale and Thornlie lines would undergo an eighteen-month shutdown for the Victoria Park-Canning Level Crossing Removal Project along the Armadale line starting in early 2023. Works would be conducted for the Thornlie–Cockburn Link during the shut down as well, such as duplication of the tracks between Beckenham junction and Thornlie station.{{cite press release |first1=Mark |last1=McGowan |first2=Rita |last2=Saffioti |title=Joint media statement – Major METRONET projects to transform the Armadale Line |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---Major-METRONET-projects-to-transform-the-Armadale-Line-20220220 |publisher=Government of Western Australia |access-date=19 July 2023 |date=20 February 2022 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164535/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/Joint-media-statement---Major-METRONET-projects-to-transform-the-Armadale-Line-20220220 |url-status=live }} In August 2022, the 18-month shutdown was delayed until late 2023, thereby delaying the completion of the Thornlie–Cockburn Link to 2025.{{cite press release |first1=Mark |last1=McGowan |first2=Rita |last2=Saffioti |title=All aboard: date set for opening of METRONET Forrestfield-Airport Link |url=https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/All-aboard:-date-set-for-opening-of-METRONET-Forrestfield-Airport-Link-20220816 |publisher=Government of Western Australia |access-date=19 July 2023 |date=16 August 2022 |archive-date=19 July 2023 |archive-url=https://web.archive.org/web/20230719164533/https://www.wa.gov.au/government/media-statements/McGowan-Labor-Government/All-aboard:-date-set-for-opening-of-METRONET-Forrestfield-Airport-Link-20220816 |url-status=live }}{{cite web |last1=Law |first1=Peter |title=Forrestfield-Airport Link set to finally open after $1.9b project suffered two years of delays |url=https://thewest.com.au/news/transport/forrestfield-airport-link-set-to-finally-open-in-october-after-two-years-of-delays-c-7894224 |website=The West Australian |access-date=19 July 2023 |date=16 August 2022 |url-access=subscription |archive-date=5 July 2023 |archive-url=https://web.archive.org/web/20230705085309/https://thewest.com.au/news/transport/forrestfield-airport-link-set-to-finally-open-in-october-after-two-years-of-delays-c-7894224 |url-status=live }} The shutdown began on 20 November 2023.{{cite web |last1=Zimmerman |first1=Josh |title=Armadale Line shutdown: Smooth-sailing on first morning but 'potentially significant' disruption to come |url=https://thewest.com.au/politics/state-politics/armadale-line-shutdown-smooth-sailing-on-first-morning-but-potentially-significant-disruption-to-come-c-12613222 |website=The West Australian |access-date=10 December 2023 |date=20 November 2023 |url-access=subscription |archive-date=1 December 2023 |archive-url=https://web.archive.org/web/20231201142647/https://thewest.com.au/politics/state-politics/armadale-line-shutdown-smooth-sailing-on-first-morning-but-potentially-significant-disruption-to-come-c-12613222 |url-status=live }}{{cite web |last1=Shepherd |first1=Briana |last2=Ho |first2=Cason |title=Perth's Armadale/Thornlie rail line closure is underway. Here's what you need to know about getting around |url=https://www.abc.net.au/news/2023-11-20/armadale-rail-closure-begins-with-major-upgrade-underway/103120976 |website=ABC News |access-date=10 December 2023 |date=20 November 2023 |archive-date=9 December 2023 |archive-url=https://web.archive.org/web/20231209113726/https://www.abc.net.au/news/2023-11-20/armadale-rail-closure-begins-with-major-upgrade-underway/103120976 |url-status=live }} Since then, various train replacement bus routes have operated.{{cite web |title=Armadale and Thornlie Line Shutdown |url=https://www.transperth.wa.gov.au/Track-Closures/Armadale-and-Thornlie-Line-Shutdown |website=Transperth |access-date=10 December 2023 |archive-date=21 August 2023 |archive-url=https://web.archive.org/web/20230821010428/https://www.transperth.wa.gov.au/Track-Closures/Armadale-and-Thornlie-Line-Shutdown |url-status=live }}

Track laying for the relocated freight railway began in mid-2023.{{cite web |title=Freight line laying underway |url=https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/freight-line-laying-underway |website=Metronet |access-date=7 September 2023 |date=22 August 2023 |archive-date=7 September 2023 |archive-url=https://web.archive.org/web/20230907084824/https://www.metronet.wa.gov.au/news/latest-news/category/thornlie-cockburn-link/freight-line-laying-underway |url-status=live }} This was completed by October 2023, with freight trains running along the new alignment at that point, allowing for tracklaying for the Thornlie line to commence.{{cite press release |first1=Roger |last1=Cook |first2=Rita |last2=Saffioti |title=Thornlie-Cockburn Link work ramps up with freight rail relocated |url=https://www.wa.gov.au/government/media-statements/Cook-Labor-Government/Thornlie-Cockburn-Link-work-ramps-up-with-freight-rail-relocated-20231024 |publisher=Government of Western Australia |access-date=24 October 2023 |date=24 October 2023 |archive-date=27 October 2023 |archive-url=https://web.archive.org/web/20231027040338/https://www.wa.gov.au/government/media-statements/Cook-Labor-Government/Thornlie-Cockburn-Link-work-ramps-up-with-freight-rail-relocated-20231024 |url-status=live }}{{cite web |title=The METRONET Thornlie-Cockburn Link (TCL) project celebrated a key milestone this week, with the relocation of Arc Infrastructure's 22km of freight rail track now complete, enabling works on the new passenger rail to ramp up. |url=https://www.arcinfra.com/Newsroom/Freight-rail-relocation-helps-METRONET-ramp-up |website=Arc Infrastructure |access-date=12 November 2023 |date=25 October 2023 |archive-date=12 November 2023 |archive-url=https://web.archive.org/web/20231112133921/https://www.arcinfra.com/Newsroom/Freight-rail-relocation-helps-METRONET-ramp-up |url-status=live }} The first train ran on the Thornlie–Cockburn Link on 20 January 2025.{{cite press release |last1=Cook |first1=Roger |last2=Saffioti |first2=Rita |title=First train on the tracks as METRONET Thornlie-Cockburn Link reaches milestone |url=https://www.wa.gov.au/government/media-statements/Cook%20Labor%20Government/First-train-on-the-tracks-as-METRONET-Thornlie-Cockburn-Link-reaches-milestone-20250120 |publisher=Government of Western Australia |access-date=20 January 2025 |date=20 January 2025}}{{cite web |last1=Caporn |first1=Dylan |title=State election: Premier Roger Cook seeks to wedge Liberals leader Libby Mettam over flat Perth fares |url=https://thewest.com.au/politics/state-politics/state-election-premier-roger-cook-seeks-to-wedge-liberals-leader-libby-mettam-over-flat-perth-fares-c-17444470 |website=The West Australian |access-date=20 January 2025 |date=20 January 2025 |url-access=subscription}}{{cite web |last1=Vinci |first1=Caitlin |title=Metronet reaches milestone as test train travels from Nicholson Road station along Thornlie-Cockburn link |url=https://www.perthnow.com.au/local-news/metronet-reaches-milestone-as-test-train-travels-from-nicholson-road-station-along-thornlie-cockburn-link-c-17397925 |website=PerthNow |access-date=26 January 2025 |date=24 January 2025}} The line is planned to reopen on Sunday, 8 June 2025, with a community event to be held on that day. Regular services will commence the following day.{{cite press release |last1=Cook |first1=Roger |last2=Saffioti |first2=Rita |title=Joint media statement – Opening date set for Thornlie–Cockburn Link and inner Armadale Line elevated rail stations |url=https://www.wa.gov.au/government/media-statements/Cook%20Labor%20Government/Joint-media-statement---Opening-date-set-for-Thornlie-Cockburn-Link-and-inner-Armadale-Line-elevated-rail-stations-20250330 |publisher=Government of Western Australia |access-date=30 March 2025}}

According to the Perth and Peel @ 3.5 Million plan, the Thornlie line will eventually form part of a southern loop line around Perth by a link from the Airport line to the Thornlie line and a link from the Thornlie line to the Fremantle line.{{cite web |title=Perth and Peel@3.5million: The Transport Network |url=https://www.transport.wa.gov.au/mediaFiles/projects/PROJ_P_Perth_Peel_3.5million_TransportNetwork.pdf |website=Department of Transport |access-date=13 May 2023 |pages=20, 23, 26 |date=March 2018 |archive-date=15 March 2023 |archive-url=https://web.archive.org/web/20230315162918/https://www.transport.wa.gov.au/mediaFiles/projects/PROJ_P_Perth_Peel_3.5million_TransportNetwork.pdf |url-status=live }}

The Thornlie branch uses {{track gauge|1067mm|lk=on}} narrow gauge track{{cite web |last1=Laird |first1=Philip |title=Perth's urban rail renaissance |url=https://ro.uow.edu.au/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1278&context=eispapers1 |website=University of Wollongong |access-date=14 July 2023 |pages=4, 7 |archive-date=6 March 2022 |archive-url=https://web.archive.org/web/20220306074937/https://ro.uow.edu.au/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1278&context=eispapers1 |url-status=live }} and has a maximum speed of {{convert|110|km/h}}. Trains are powered by {{25 kV 50 Hz}} overhead line equipment which is powered by a substation in Beckenham. The Thornlie line branch is single-tracked except at Thornlie station, which has two tracks. The Thornlie line is the only section of the Transperth network that is single-tracked.

The Thornlie line uses fixed block signalling. As part of Metronet's High Capacity Signalling Project, the Transperth rail network will be upgraded to moving block signalling using communications-based train control (CBTC).{{cite web |title=High Capacity Signalling Fact Sheet |url=https://www.metronet.wa.gov.au/Portals/31/High%20Capacity%20Signalling%20Fact%20Sheet.pdf |website=Metronet |access-date=18 July 2023 |page=2 |archive-date=30 March 2023 |archive-url=https://web.archive.org/web/20230330184800/https://metronet.wa.gov.au/Portals/31/High%20Capacity%20Signalling%20Fact%20Sheet.pdf |url-status=live }}{{cite web |title=METRONET: High Capacity Signalling |url=https://www.infrastructureaustralia.gov.au/map/metronet-high-capacity-signalling |website=Infrastructure Australia |access-date=18 July 2023 |archive-date=5 July 2023 |archive-url=https://web.archive.org/web/20230705085313/https://www.infrastructureaustralia.gov.au/map/metronet-high-capacity-signalling |url-status=live }} As of 2021, the CBTC system is planned to be implemented on the Armadale and Thornlie lines by June 2031.{{cite web |title=HCS SWTR Book 1 – Scope of Works DRAFT 01-09-21_Redacted |url=https://www.tenders.wa.gov.au/watenders/tender/display/tender-details.do?id=50712&action=display-tender-details&returnUrl=%2Ftender%2Fsearch%2Ftender-search.do%3FCSRFNONCE%3D2C8CC45A3E0537F33C62E60CB6DF5A30 |website=Tenders WA |access-date=20 January 2022 |date=30 September 2021 |pages=18, 77, 79, 120 |archive-date=20 January 2022 |archive-url=https://web.archive.org/web/20220120061042/https://www.tenders.wa.gov.au/watenders/tender/display/tender-details.do?id=50712&action=display-tender-details&returnUrl=%2Ftender%2Fsearch%2Ftender-search.do%3FCSRFNONCE%3D2C8CC45A3E0537F33C62E60CB6DF5A30 |url-status=live }} Click Download Now, then Download for Information Only. Make sure HCS SWTR Book 1 – Scope of Works DRAFT 01-09-21_Redacted.pdf is selected, then click Download Documents.

File:Thornlie Station, Western Australia, B-series at platform 2, July 2021.jpg at platform 1|alt=Brick train station with side platforms and a train parked on the left platform]]

File:Randford rd station GN 022024-14.jpg

Until the temporary closure, Thornlie line trains stopped at 11 stations in total. Thornlie station currently has a {{convert|100|m|adj=on}} long platform, but it will be lengthened as part of the Thornlie–Cockburn Link to {{convert|150|m}}, long enough for six-car trains, the longest trains on the Transperth network. All the new station platforms and the Cockburn Central station platform will be long enough for six-car trains as well. Train lengths will be restricted by {{convert|100|m|adj=on}} long platforms on the Armadale line, although these are planned to be lengthened eventually to allow for six car-trains on the Thornlie line.{{rp|12, 40}} The first platforms to be extended are planned to be at Claisebrook and Victoria Park.{{cite web |title=Platform and Signalling Upgrade Program Phase 1 and Phase 2 Upgrades Project: Summary Assessment Report |url=https://prod-iwa-public-files.s3.ap-southeast-2.amazonaws.com/public/2024-07/Platform%20and%20Signalling%20Upgrade%20Program%20-%20Phase%201%20and%202%20Upgrades%20-%20Public%20Transport%20Authority%20-%20MIPA%20Summary%20Assessment%20Report.pdf |website=Infrastructure Western Australia |access-date=11 July 2024 |date=January 2024}}{{cite web |last1=Mckenzie |first1=Matt |title=Metronet: Armadale, Midland, Fremantle lines need longer platforms to take upgraded trains |url=https://thewest.com.au/business/infrastructure/metronet-armadale-midland-fremantle-lines-need-longer-platforms-to-take-upgraded-trains-c-15316045 |website=The West Australian |access-date=11 July 2024 |date=11 July 2024 |url-access=subscription}} All stations from Perth to Oats Street are within fare zone one, all stations from Queens Park to Ranford Road are within fare zone two, and Cockburn Central station is within fare zone three.

Transperth train services are operated by the Public Transport Authority's Transperth Train Operations division.{{cite web |title=Transperth |url=https://www.pta.wa.gov.au/our-services/transperth |website=Public Transport Authority |access-date=18 July 2023 |archive-date=5 October 2021 |archive-url=https://web.archive.org/web/20211005173906/https://www.pta.wa.gov.au/our-services/transperth |url-status=live }} Thornlie line services have been suspended since 20 November 2023; these are planned to recommence in mid-2025. Thornlie line trains ran every 15 minutes during the day on all days except Sunday, when they ran every 30 minutes.{{cite web |title=Armadale/Thornlie Line Train Timetable |url=https://www.transperth.wa.gov.au/timetablepdfs/Armadale%20Thornlie%20Line%2020221010.pdf |website=Transperth |access-date=18 July 2023 |archive-date=26 March 2023 |archive-url=https://web.archive.org/web/20230326212850/https://www.transperth.wa.gov.au/timetablepdfs/Armadale%20Thornlie%20Line%2020221010.pdf |url-status=live }} This made the Thornlie line Transperth's least frequent line. At night, frequencies reduced to every half an hour, and every hour late at night. Thornlie line peak frequencies are forecast to remain the same until at least 2031, with capacity increases to be provided for by longer trains enabled by platform lengthening.{{rp|12}}{{cite web |title=WA Railcar Program Project Definition Plan |url=https://www.metronet.wa.gov.au/Portals/31/Project%20Documents/Railcars/Railcar%20Project%20Definition%20Plan%20.pdf |website=Metronet |access-date=18 July 2023 |page=10 |archive-date=18 January 2022 |archive-url=https://web.archive.org/web/20220118183225/https://www.metronet.wa.gov.au/Portals/31/Project%20Documents/Railcars/Railcar%20Project%20Definition%20Plan%20.pdf |url-status=live }} Operating hours were from roughly 5:00 am to midnight. Thornlie line trains stopped at every station along the Armadale line between Perth and Cannington stations, except for Perth Stadium station, which was typically only served by Armadale line trains. This contrasts with Armadale line trains, which typically skipped most stations along that section, except McIver, Claisebrook, and Oats Street stations. Between Cannington and the Thornlie branch is Beckenham station, which was skipped by Thornlie line trains.

File:Transperth A-Series 40 @ Thornlie Station.jpg at Thornlie station, November 2018|alt=Close up view of a train stopped at a train station platform]]

The Thornlie line was served primarily by Transperth A-series trains, with Transperth B-series trains occasionally used as well. By 2031, it is planned that all A-series trains will be retired, leaving the Thornlie line to be served primarily by B-series trains.{{rp|24}} The A-series trains were built between 1991 and 1999 and consist of two cars which are usually joined to form four-car trains. Each car has two doors on each side.{{cite web |author1=AECOM |title=A-Series EMU Railcar Review |url=https://www.parliament.wa.gov.au/publications/tabledpapers.nsf/displaypaper/3912874cc5fc39f2e6de87f348257e440005910a/$file/tp-2874.pdf |website=Parliament of Western Australia |access-date=8 March 2024 |page=21 |date=April 2015 |archive-date=20 January 2021 |archive-url=https://web.archive.org/web/20210120105100/https://www.parliament.wa.gov.au/publications/tabledpapers.nsf/displaypaper/3912874cc5fc39f2e6de87f348257e440005910a/%24file/tp-2874.pdf |url-status=live }} The B-series trains were built between 2004 and 2019, consist of three cars each and have two doors on the side of each car.{{cite web |url=https://railknowledgebank.com/Presto/content/GetDoc.axd?ctID=MTk4MTRjNDUtNWQ0My00OTBmLTllYWUtZWFjM2U2OTE0ZDY3&rID=NTE2&pID=Nzkx&attchmnt=True |last1=Gearon |first1=Elwyn |last2=Holden |first2=Graham |title=New Metro Rail: Perth 'B' Series Electric Multiple Units |publisher=Engineers Australia |via=Rail Knowledge Bank |date=September 2008 |access-date=8 March 2024 |archive-date=8 March 2024 |archive-url=https://web.archive.org/web/20240308130716/https://railknowledgebank.com/Presto/content/GetDoc.axd?ctID=MTk4MTRjNDUtNWQ0My00OTBmLTllYWUtZWFjM2U2OTE0ZDY3&rID=NTE2&pID=Nzkx&attchmnt=True |url-status=live }} These trains are all primarily stored at Claisebrook depot.

{{further|Armadale line#Patronage}}

Thornlie station had 578,199 boardings in the 2013–14 financial year.{{cite web |title=Question On Notice No. 4248 asked in the Legislative Assembly on 25 June 2015 by Mr M. Mcgowan |url=https://www.parliament.wa.gov.au/parliament/pquest.nsf/viewLAPQuestByDate/86E328F41D2F80B348257E6E002927CE |website=Parliament of Western Australia |access-date=18 July 2023 |archive-date=20 August 2023 |archive-url=https://web.archive.org/web/20230820084219/https://parliament.wa.gov.au/parliament/pquest.nsf/viewLAPQuestByDate/86E328F41D2F80B348257E6E002927CE |url-status=live }} When the Thornlie–Cockburn Link opens, the line is predicted to have 12,225 boardings per day, rising to 17,425 boardings per day in 2031.{{rp|12}}

{{notelist}}

{{reflist}}

{{commons}}

• [https://web.archive.org/web/20070829042053/http://www.newmetrorail.wa.gov.au/Default.aspx?tabid=79 Thornlie Spur Line] on the New MetroRail website (archive)
• [https://web.archive.org/web/20070828222936/http://www.newmetrorail.wa.gov.au/Default.aspx?tabid=137 Local Area Updates] on the New MetroRail website (archive)
• [https://www.metronet.wa.gov.au/projects/thornlie-cockburn-link Thornlie–Cockburn Link] on the Metronet website
• [https://www.epa.wa.gov.au/sites/default/files/EPA_Report/Thornlie-Cockburn%20Link%20-%20EPA%20Report.pdf Thornlie–Cockburn Link environmental assessment] by the Environmental Protection Authority

{{Perth public transport}}

{{Public Transport Authority of Western Australia railway stations|Thornlie–Cockburn=y}}

{{Railway lines in Western Australia}}

Category:Transperth railway lines

Category:Railway lines opened in 2005

Category:3 ft 6 in gauge railways in Australia

Category:25 kV AC railway electrification