Spur to Thornlie

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 in Beckenham, 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.^[1]

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 Beckenham tunnel was built and Albany Highway was grade separated from the freight railway.^[2] The 200-metre (660 ft) long Glen Iris tunnel was also constructed as part of an extension of the Kwinana Freeway in 2000.^[3][4]

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 Beckenham tunnel. A new master plan was released in 2002. 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.^[5]

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. The second stage contract for the Beckenham tunnel was awarded to John Holland Group in March 2003 at a cost of A$14.225 million. The second stage consisted of 380 metres (1,250 ft) of tunnel; the realignment of 1.4 kilometres (0.87 mi) 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 440 metres (1,440 ft).^[6][7] 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 million.^[8][9] Other work involved relocating BP's Kewdale White Oil Line,^[10] which is a pipeline that carries fuel from the Kwinana import terminal to Perth Airport via the freight railway.^[11]

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, 2.9 kilometres (1.8 mi) 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,^[12] but that was extended to 16 December 2003.^[10] 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 million. By then, the planned opening date was February 2005.^[13][14] Construction had begun by July 2004.^[15] 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.^[16][17] Full service began on 8 August 2005.^[18]

Thornlie–Cockburn Link extension

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.^[19][20] The Liberal Party won the election, so that plan did not go ahead.^[21] In 2015, RAC WA called for the Thornlie line to be extended to Cockburn Central station on the Mandurah line.^[22] 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 million.^[23][24]

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 million and be open in late-2023,^[25][26][27] whereas Labor said it could be constructed for $474 million by 2021 as part of its revised Metronet plans.^[28][29] Labor won the 2017 election and planning for the Thornlie–Cockburn Link began in late-March 2017.^[30] 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.^[31] The September 2017 state budget gave the Thornlie–Cockburn Link a cost of $535.8 million.^[32][33]

The business case for the Thornlie–Cockburn Link was submitted to Infrastructure Australia in August 2017.^[34] 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 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.^[35][36][37] The Infrastructure Australia assessment allowed $700 million in federal funding to be spent on the Thornlie–Cockburn Link and the Yanchep Rail Extension, of which $350 million was for the Thornlie–Cockburn Link.^[38][39]

Enabling legislation was introduced to the Parliament of Western Australia in May 2018^[40][41] and passed in November 2018.^[42]

Route

Stations

The Thornlie line branch has one station. Until the temporary closure, Thornlie line trains stopped at 11 stations in total.^[109] Thornlie station currently has a 100-metre (330 ft) long platform, but it will be lengthened as part of the Thornlie–Cockburn Link to 150 metres (490 ft), 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 100-metre (330 ft) long platforms on the Armadale line, although these are planned to be lengthened eventually to allow for six car-trains on the Thornlie line.^{[45]: 12, 40}

Rolling stock

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.^{[35][45]: 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.^[117] 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.^[118] These trains are all primarily stored at Claisebrook depot.^[35]

Patronage

Thornlie station had 578,199 boardings in the 2013–14 financial year.^[119] 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.^[45]: 12