Railway Spirals

A spiral (sometimes called a spiral loop or just loop) is a technique employed by railways to ascend steep hills. A railway spiral rises on a steady curve until it has completed a loop, passing over itself as it gains height, allowing the railway to gain vertical elevation in a relatively short horizontal distance. It is an alternative to a zig-zag, and avoids the need for the trains to stop and reverse direction while ascending. If the train is longer than the length of each loop it may be possible to view it looping above itself.

The term "loop" is also often used for a railway that curves sharply and goes back on itself: if the railway crosses itself, then it forms a spiral or helix; otherwise, it forms the much more common horseshoe curve or bend.

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.

Cougal Spiral, Kyogle, New South Wales

The Cougal Spiral is a heritage-listed single track railway tunnel and spiral feature of the New South Wales North Coast railway line that connects New South Wales with Queensland through Richmond Gap. It was built during 1930. It is also known as the Border Loop railway formation and landscape, Cougal To Border Loop and Railway Spiral and Landscape. The railway line needs to climb at a steady ruling gradient from Kyogle to the summit at a 1100 metre tunnel at the border between the two states. The border is also at the watershed. The rail spiral and associated facilities are located between 871 and 876 kilometres from Sydney Central railway station.