Unanderra – Moss Vale railway line

The Unanderra – Moss Vale railway line is a cross country railway line in New South Wales. The line branches from the Illawarra (South Coast) railway line at the town of Unanderra and winds west over the Illawarra escarpment to the Southern Highlands town of Moss Vale. The line is one of the most scenic in New South Wales, and for the first 20 km after leaving Unanderra has an almost continuous grade 1 in 30 providing spectacular view over the Illawarra coastline.

Course
The length of the line is 57 kilometres, and is double track from Unanderra to Dombarton. The line is single track thereafter with several crossing loops. The double track section was built as part of the now abandoned Maldon to Dombarton railway line, and unfinished staunchions line this section as part of the proposed electrification.

The line has the following intermediate stations, which are all closed, apart from the occasional heritage train:
 * Dombarton - end of double line (formerly the site of an unusual crossing arrangement )
 * Summit Tank (platform & crossing loop)
 * Mount Murray (crossing loop reopened 1980s)
 * Ocean View (closed 1968)
 * Ranelagh House (platform only)
 * Robertson (platform & crossing loop)
 * Burrawang (closed 1975)
 * Calwalla (closed 1976, but crossing loop reopened 1980s)

History
The line was first proposed in the 1880s by residents of Moss Vale and local industry keen for a connection to the port at Port Kembla. Construction began on 26 June 1925, and was completed on 20 August 1932.

The line initially carried mainly limestone from the Marulan Quarry to Port Kembla Steelworks, but also vegetables from Robertson to Sydney and later, coal. Daily steam-hauled passenger trains operated from 1932, which were later replaced by diesel hauled trains, then rail-motors. A weekend excursion train operated until the early 1990s, prior to its replacement by the privately operated Cockatoo Run steam hauled weekend tourist train. This train, operated by 3801 Limited continues to operate to the present day but is hauled by a diesel electric locomotive and only runs on selected Sundays.

A section of the line was deviated in the 1960s to avoid the site of a new lake built for water supply and power generation purposes.

On 22 April 2017, a grain train lost control while descending the grade towards Unanderra. This was caused by the driver making too many brake applications within a short time, meaning the train's brake system could not recharge fast enough. The train reached a maximum speed of 107km/h, but did not derail and stopped safely on the Illawara line north of Unanderra.

On 15 December 2020, another grain train derailed under almost identical circumstances (same operator, similar location, same direction).

Operation
Freight trains continue to use the line to this day. The line remains a valuable freight link to the Wollongong area and a useful bypass line when the Main South Line is closed for trackwork. NSW TrainLink XPT services to and from Melbourne can also use this diversion, however this is rare as no XPT crew are qualified to operate on this line, so a pilot is required.

NSW TrainLink coaches (as part of the NSW TrainLink Regional Southern line) now replace the former passenger service. There are four coaches per day in both directions. The coaches stop at: The line is now operated by ARTC (Australian Rail Track Corporation), as part of its 99 year lease of the major regional lines. It is controlled from ARTC's Network Control Centre South (NCCS) at Junee.
 * Wollongong
 * Dapto
 * Albion Park
 * Burrawang
 * Robertson
 * Bowral
 * Moss Vale
 * Exeter (one service only)
 * Bundanoon (one service only)

Maldon-Dombarton Line
In 1983 State Rail began construction of a line connecting Maldon, on the Southern Highlands line near Picton, with Dombarton near Port Kembla. Construction ceased in 1988. The project would have created the longest tunnel in Australia (at the time): the 4km Avon Tunnel. Part of the incomplete tunnel, as well approaches to a bridge over the Cordeaux River, are visible today.

In 2009 a pre-feasibility report into completing the line was conducted by the Commonwealth Government which found the project could be viable. Following the report a full feasibility study was conducted. The study has been completed but has not yet been released. A spokesperson for the federal Infrastructure and Transport Minister Anthony Albanese said it would be released when "properly considered".