The Werribee line is a commuter railway line in the city of Melbourne, Victoria, Australia. Operated by Metro Trains Melbourne, it is the city's ninth longest metropolitan railway line at . The line runs from Flinders Street station in central Melbourne to Werribee station in the south west, serving 17 stations via Footscray, Newport, and Altona. The line operates for approximately 19 hours a day (from approximately 5:00 am to around 12:00 am) with 24 hour service available on Friday and Saturday nights. During peak hour, headways of up to 5–20 minutes are operated with services every 20–30 minutes during off-peak hours. Trains on the Werribee line run with a two three-car formations of Comeng, Siemens Nexas, and X'Trapolis 100 trainsets. Part of the line initially opened in 1857 by the Geelong and Melbourne Railway Company. The line was progressively finished within the next two years, allowing trains to travel from Melbourne to Geelong. In April 1885, a short branch was opened off the Werribee line just past Newport to Williamstown Racecourse, and in November 1888, a branch was opened off the Racecourse branch to Altona, terminating at a station named Altona Beach. The construction of these lines played improtant parts in the development of Geelong and Melbourne's west during the 19th and 20th centuries, with the line continuing to be an important asset in the 21st century. Since the 2010s, due to the heavily utilised infrastructure of the Werribee line, improvements and upgrades have been made. Works have included replacing sleepers, upgrading signalling technology, the removal of level crossings, planning for new infrastructure, the introduction of new rolling stock, and station accessibility upgrades. In 1857, the Geelong and Melbourne Railway Company (G&MRC) opened the Werribee to Little River section of the line they were building between Newport and Geelong, then in June of that year, they opened the section between Werribee and a temporary station near Newport, known as Greenwich.