Mandurah line

The Mandurah line, which is also known as the Southern Suburbs Railway and the South West Metropolitan Railway, is a suburban railway line and service that links the central business district (CBD) of Perth, Western Australia, with Mandurah to the south. Western Australia's Public Transport Authority (PTA) operates the line, which is 70.8 kilometres (44.0 mi) long and has 13 stations, as part of the Transperth system. The line provides a through service from the Yanchep line in the north, and includes two stations in the William Street tunnel under the CBD. It continues south to the median strip of the Kwinana Freeway, where five of its stations are located, then diverges from the freeway for the southernmost six stations in the cities of Kwinana, Rockingham and Mandurah.

Early planning for the Mandurah line began in 1989 whilst the Yanchep line was being planned. In 1994, planners chose a route branching off the Armadale line at Kenwick to follow the Kwinana freight railway and Kwinana Freeway was selected, but after the election of a Labor state government in 2001, the planned route was changed to go via a tunnel under the CBD. The Mandurah line, which was built as part of the New MetroRail project, was divided into seven major contract packages. It was designed similarly to the Yanchep line, using widely spaced stations with bus interchanges and large park-and-rides.

Construction began in February 2004; it was disrupted by labour strikes and technical issues, particularly on the CBD tunnel section. The William Street tunnel, which was originally planned to open between Perth and Warnbro station in 2006, and between Warnbro and Mandurah in 2007, opened on 15 October 2007, and the rest of the line opened on 23 December 2007. The total cost of New MetroRail was A$1.725 billion. Two infill stations have since opened: Aubin Grove in April 2017 and Lakelands in June 2023. In June 2025, the Thornlie line was extended to Cockburn Central station on the Mandurah line, completing the Kenwick route that was planned before 2001.

B-series and C-series trains are the main rolling stock used on the Mandurah line, and A-series trains were also formerly common. Trains run at a fifteen-minute headway, reducing to as short as a five-minute headway in peak times, when some services terminate at Cockburn Central. The travel time from Perth to Mandurah is 54 minutes. The line's patronage has significantly exceeded expectations, reaching a high of 23,075,517 boardings in the 2024–25 financial year, making it the busiest Transperth railway line.