page_title: Main Line railway, Queensland
section_title: First tunnels
hierarchical_section_title: Main Line railway, Queensland / History / First tunnels
caption_attribution_description: English: QR heritage loco A10 no. 6 on the Main Line to Toowoomba ~1990
context_page_description: 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 Brisbane and extends west 161 km 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, the Lockyer Creek Railway Bridge and Swansons Rail Bridge are also heritage listed.
context_section_description: Beyond Grandchester, the line was built with curves of 5 chains (100 m) radius and uncompensated grades of 1 in 50 (2%), giving an effective grade of 1 in 41 (~2.5%) on 100 m (5.0 chains) radius curves. Two tunnels were required on the section to Laidley, known as ‘Six Chain’ (either because it is situated on a 6 chains or 120 m radius curve, or because it is 6 chains or 120.7 m to be exact) long, or both) and ‘Victoria’ after the English Queen of the day. The latter is 540 m (1,770 ft) 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 (1 in 100 maximum grades) easy country to Gatton (opened 1 June 1866) and Helidon (opened 30 July 1866). This 38 km (24 mi) section was duplicated in 1913-14, with the section from Laidley to Yarongmulu (just west of the Victoria Tunnel) being built to 1 in 60 for Brisbane bound trains.
caption: This train is the maximum load an A10 class can haul up the 1 in 50 grades of the Main Line
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