Tracks diverging at the start of the spiral
When the line was duplicated in the 1940s, an 8.9 kilometre spiral deviation was built. The spiral makes use of local geography in the shape of a convenient hill which the uphill line spirals around and has short tunnels. The spiral increased the distance traveled by uphill (northbound) trains by about two kilometres. Downhill (southbound) trains continue to use the original line. The ruling gradient of the new uphill line is 1 in 66.
Due to the extensive blasting required to create 27 metre cuttings through granite, the line suffered from rockfalls with twelve significant falls between 1960 and 1987. In January 1994, the spiral line closed for a four-month rebuild which saw the cuttings widened and regraded to benched 55 degree slopes as part of the One Nation project.
- Bethungra Spiral NSWrail.net
- Bethungra - Frampton SA Track & Signal
- "The Bethungra Spiral Rectification Project" Railway Digest June 1994 pages 12-15
- "Doubling, Deviation & New Construction Works" Railway Gazette 18 July 1941 page 54
- "Main-Line Deviation in Australia" Railway Gazette 14 January 1949 pages 42-45
- "Bethungra Spiral". Railway Digest. May 2014. p. 39.
Media related to Bethungra Spiral at Wikimedia Commons
- "Bethungra Spiral (listing NSW5011929)". Australia Heritage Places Inventory. Department of Sustainability, Environment, Water, Population and Communities. Retrieved 2008-08-13.