Bethungra Spiral
Tracks diverging at the start of the spiral
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| Opened | 1946 |
The Bethungra Spiral is a rail spiral, built on the Main South line of New South Wales in Australia at Bethungra between Cootamundra and Junee.
The original line was graded at 1 in 40 for Sydney bound trains, which imposed a severe limitation on train loads, and also caused congestion as bank engines were attached.
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.
Coordinates: 34°45′S 147°53′E / 34.75°S 147.88°E
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