Mandurah line

The Mandurah line is a commuter railway and service on the Transperth network in Western Australia that runs from Perth south to the state's second largest city Mandurah. The service is operated by Transperth Train Operations, a division of the Public Transport Authority. The line is 70.1 kilometres (43.6 mi) long and has 12 stations. At its northern end, the line (travelling south) begins as a continuation of the Joondalup line at Perth Underground, and (travelling north) ends as a continuation of the Joondalup line at Elizabeth Quay. The first 1.3 kilometres (0.81 mi) of the line is underground, passing under the Perth central business district. The line surfaces and enters the median of the Kwinana Freeway just north of the Swan River. It continues south down the freeway's median for 30 kilometres (19 mi), before veering south-west towards Rockingham. The final stretch of the line goes south from Rockingham to Mandurah.

Planning for a railway line to Mandurah began in the early 1990s, during the construction of the Joondalup line. The first route proposed was an extension of the Fremantle line to Mandurah passing directly through the Rockingham town centre. The preferred route was later changed to a spur off the Armadale line at Kenwick via Thornlie for reasons of cost. Following a change in state government in 2001, the route was changed again, this time to a direct route along the Kwinana Freeway south of Perth with Rockingham station relocated to align with the more direct route. Construction began in March 2004. The underground portion of the line, between Perth and Esplanade station, was the first section to open. It began operating on 15 October 2007. The rest of the line opened on 23 December 2007. Two new stations have since been opened in 2017 and 2023, with a third station currently in planning. The line will be connected to the Armadale line via Cockburn Central and the Thornlie line.

Trains take 51 minutes to get from Perth Underground to Mandurah station. The line is the busiest on the Transperth network, with 17,669,846 boardings in the 2022–23 financial year. Headways are at least every 15 minutes during the day, rising to every 5 minutes on parts during peak time.