Bethungra Spiral, New South Wales

About 23 km south of Cootamundra near the main road between Cootamundra and Wagga is one of Australia's most unusual pieces of railway engineering. The Sydney to Melbourne railway line spirals around Bethungra Hill, crossing itself and the line north line while traversing some of the deepest cuttings in Australia. Created in the 1940s, the Heritage-listed Spiral takes the line through two tunnels and over the top of the hill, and through a big cutting at the spur. The original single-track line, opened in 1878, 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 and detached.



When the line was duplicated in the late 1940s, an 8.9 kilometre spiral deviation was built. The spiral makes use of local geography in the shape of a convenient hill around which the uphill ("up", or Sydney-bound) track spirals in order to gain the necessary height over a longer distance, thus giving a lesser gradient. However, the fact that the hill is on the "down" (southbound) side of the original track necessitated two crossings of the original line by the new northbound track — one a tunnel to take it to the eastern (or "down") side of the original track in order to then spiral around the hill, and a viaduct beyond the spiral to take the new track back to the left hand side of the original line, as Australian trains run on the left, as in the UK, France and Japan. The Spiral has two short tunnels, one already mentioned at the beginning of the Spiral, for the "up" track to cross beneath the original line to reach the "down" side, and a second tunnel that allows it to pass over itself at a later point in the Spiral, having circled the hill to gain height.

The spiral increased the distance travelled 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 deep cuts through granite, the line suffers from rockfalls, with twelve significant falls happening between 1960 and 1987. In January 1994, the spiral line closed for a four-month rebuild, which saw the cuts widened and regraded to benched 55 degree slopes as part of the One Nation project.

A traveller who has just passed through Bethungra township on the way to Cootamundra would be unaware of the existence nearby of the Bethungra Spiral, to the right of the Olympic Highway, as there is no signage or safe off-road parking to observe the two tracks at three different elevations. However there is a point at which three railway tracks can be seen at three different heights on the adjacent hillside to the east of the Olympic Highway. The bottom and top tracks are the "up" (northbound) track before and after it has crossed the "down" (southbound) track and traversed the Spiral, while the middle track is the original single-track line, which is now the "down" (southbound) track.