Longest railway spiral

The most convoluted section of railway is the Dulishan Spiral, which forms part of the Alishan Forest Railway, a narrow-gauge scenic railway originally built in 1912 to serve the logging industry in Chiayi County, Taiwan, China. The start and end of the Dulishan Spiral are only 570 m (1,870 ft) apart, but separated by an elevation difference of 233 m (764 ft). As a result, trains traveling between the villages of Zhangnaoliao and Shibijao have to negotiate 5.1 km (3.1 mi) of twisting track to cover that 570 m straight-line distance.

Because adhesion railways (which use only the friction of steel wheels on steel track) struggle with steep grades – the steepest they can manage is a grade of around 9% (1 in 11) – railways negotiating tough terrain often have to use features called "loops" or "spirals". These are track layouts in which the train goes on lengthy diversions, often involving tunnels and viaducts, in order to smooth out a drastic change in elevation. Famous examples of this include Horseshoe Curve in the Allegheny Mountains, Pennsylvania, USA, and the Raurimu Spiral on New Zealand's North Island.

The Alishan Forest Railway features many such features, include several switchbacks (in which the train zig-zags its way up hillsides) and loops. None compare to the Dulishan Spiral, however, which features 11 tunnels and involves the track crossing over itself 10 times.