Main railway line
The Main Line is a railway line in South East Queensland, Australia. It was opened in a series of sections between 1865 and 1867. It commences at Roma St Station in the Brisbane central business district and extends west to Toowoomba. It is the first narrow gauge main line constructed in the world. The section of the line from the end of Murphys Creek railway station to the Ruthven Street overbridge, Harlaxton is listed on the Queensland Heritage Register. The Murphys Creek Railway Complex, the Lockyer Creek Railway Bridge (Lockyer), the Lockyer Creek Railway Bridge (Murphys Creek),Swansons Rail Bridge and Bremer River Rail Bridge are also heritage listed.
History
Ipswich to Grandchester
The colony of Queensland separated from New South Wales in 1859, and the new government was eager to facilitate development and immigration. As adequate river transport was already established between the capital Brisbane and Ipswich, improved transport to the fertile Darling Downs region situated west of Toowoomba was seen as a priority. As such, construction of the railway commenced from Ipswich heading west over relatively flat, easy country opened to Bigge's Camp, at the eastern base of the Little Liverpool Range. The only significant engineering work for this section was the bridge over the Bremer River to North Ipswich. This first section opened on 31 July 1865, and was named the Main Line.The line was built by the Queensland government to the unusual gauge of ; at the time this being the only narrow gauge main line in the world.
The line largely followed the alignment surveyed by a private company, the Moreton Bay Tramway Company, which had proposed to build a horse-drawn tramway but had been unable to raise funds to do so beyond an initial start on earthworks.
The adoption of narrow gauge was controversial at the time, and was largely predicated by the government's desire for the fastest possible construction timeframe at least cost. This resulted in adoption of sharper curves and a lower axle load than was considered possible using standard gauge, and an assessment at the time put the cost of a narrow gauge line from Ipswich to Toowoomba as 25% of the cost of a standard gauge line. In a colony with a population of ~30,000 when the decision was made, it is understandable.
First tunnels
Beyond Grandchester, the line was built with curves of radius and uncompensated grades of 1 in 50, giving an effective grade of 1 in 41 on radius curves. Two tunnels were required on the section to Laidley, known as 'Six Chain' and 'Victoria' after the English Queen of the day. The latter is long, and both remain in service, being the oldest single track railway tunnels still in use in Australia.From the western portal of the Victoria tunnel the line descends at 1 in 50 to Laidley and then over relatively flat easy country to Gatton and Helidon. This section was duplicated in 1913–14, with the section from Laidley to Yarongmulu being built to 1 in 60 for Brisbane bound trains.
Surmounting the main range
From Helidon the line climbs in up the Main Range to the summit at Harlaxton at an average grade of 1 in 70. However, as the maximum grade is 1 in 50 uncompensated with radius curves, the ruling equivalent grade is 1 in 41, and the maximum speed on the entire section is. This section was opened on 30 April 1867. As built the section contained 157 cuttings, 128 embankments, 47 bridges, 175 culverts, 9 tunnels, 49 curves of radius and a further 77 curves between and radius, with a total length of, or 68% of the section.Comment on the design
A 1995 report commissioned by QR to investigate improving the clearance through the tunnels so high ISO containers could be accommodated includes a section commenting on the original design. It states that:
In relation to the Main Range section, it said:
In 2013 QR called tenders for the lowering of the 11 tunnel floors to enable ISO containers to be carried when the work is completed. The work was completed in 2020 during the COVID-19 shutdown. It also enabled QPB Baggage and Power Cars to be used on the Westlander between Brisbane and Charleville.
East to the Capital
The early realisation by the Queensland government of the advantages of rail transport over river transport resulted in the line soon being extended east towards Brisbane. The line was extended from Ipswich to Oxley West on 5 October 1874, and Oxley's Point on 4 February 1875.The section from Indooroopilly to Roma Street was constructed at the same time and opened 14 June 1875, with stations in West Milton, Toowong, and Milton. This section initially operated separate from the rest of the Main Line, until the completion of the first Albert Bridge over the Brisbane River connected the two parts on 7 July 1876. As part of that project the line west of Ipswich was realigned with a new bridge over the Bremer River at Wulkuraka opening on 26 April 1875. Part of the original line remains to access the North Ipswich Railway Workshops Museum.
In 1877, Auchenflower station opened on the line between Toowong and Milton.
In 1881, a siding was constructed on the site of the current Chelmer station, just south of what was the Riverton station.
The section from Ipswich to Roma St was duplicated between 1885 and 1887, indicating how quickly the traffic volume grew on the line. The Albert Bridge was built to accommodate two tracks in 1876, though only one was laid at the time.
In 1889, the siding at Chelmer was converted into a station, and Riverton station to the north was closed.
The 1893 flood resulted in the collapse of the first Albert Bridge, resulting in the Indooroopilly to Roma Street section again operating separately from the rest of the Main Line. Ferries were used for transport across the river to connect the two sections until the second and current Albert Bridge opened in 1895.
The line west of Ipswich was duplicated to Wulkuraka in 1902, to Grandchester in 1913 and from Yarongmalu to Helidon in 1918.
The section from Roma St to Corinda was quadruplicated in 1963, and extended to Darra in 2011, which became the junction for the first section of the new Springfield line at that time.
Current line standards
The Main Line is currently laid with rail between Roma St and Ipswich, rail west of there. The two tracks added in 1963 between Roma St and Corinda have an axle load of, the rest of the line has a axle load.The speed limit is to Rosewood, west of there except for block freight and coal trains which are limited to, and when traveling downhill from Harlaxton to Murphys Creek.
The section between Ipswich and Rosewood features bi-directional signalling.