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; otherwise, it forms the much more common horseshoe curve or bend.
A spiral loop is not the same as the transition spiral or spiral easement used to provide a transition from a tangent into a horizontal circular curve. Spiral easement is used to avoid abrupt changes in the sideward acceleration experienced by a railway vehicle and the passengers in the vehicle approaching the horizontal circular curve and to prevent abrupt forces and discomfort.
- 1 List of spirals
- 1.1 Argentina
- 1.2 Australia
- 1.3 Bulgaria
- 1.4 Canada
- 1.5 China
- 1.6 Croatia
- 1.7 France
- 1.8 Germany
- 1.9 India
- 1.10 Iran
- 1.11 Ireland
- 1.12 Italy
- 1.13 Japan
- 1.14 Kenya
- 1.15 South Korea
- 1.16 Madagascar
- 1.17 Myanmar
- 1.18 New Zealand
- 1.19 Russia
- 1.20 Serbia
- 1.21 Slovakia
- 1.22 South Africa
- 1.23 Spain
- 1.24 Sri Lanka
- 1.25 Switzerland
- 1.26 Taiwan
- 1.27 Uganda
- 1.28 United Kingdom
- 1.29 United States
- 2 See also
- 3 References
- 4 External links
List of spirals
- Spiral on the uphill track at Bethrunga on the Main Southern railway line, New South Wales. The downhill track remains on the original steep plain 1 in 40 gradient.
- Spiral on the single track at Cougal on the North Coast railway line, New South Wales.
- Four Spirals on the Rhodope Mountain Line between Septemvri to Dobrinishte railway 760 mm (2 ft 5 15⁄16 in) gauge between Velingrad and Cherna Mesta at , , and .
- Spiral just outside Klisura at on the Sofia to Tulovo railway.:110
- Spiral just outside Radevtsi at on the Ruse to Dimitrovgrad railway.:110
- Double spiral just outside Raduntsi at on the Ruse to Dimitrovgrad railway.:110
- Double spiral at Big Hill at on the approach to Kicking Horse Pass on the Canadian Pacific Railway route.
- There used to be a spiral at Trinity, Newfoundland on the former Newfoundland Railway.
- There used to be a spiral at Rogers Pass at that was superseded when the Connaught Tunnel (British Columbia) was built.
- Spiral South of Baoji at on the Baocheng line.
- Spiral South of Baishiyan at Chengkun line. on the
- Spiral at Lewu at on the Chengkun line.
- Spiral at Wazu at on the Chengkun line.
- Spiral at Tiekou at on the Chengkun line.
- 2 spirals near Heijing at on the Chengkun line.
- Spiral at Shangshali at Binzhou line. on the
- There used to be a series of spirals on the Nanjiang line between Turpan and Korla. This line was rebuilt on a shorter route in 2014.
- There used to be a spiral at Guanjiao at Qingzang line. (see photo). on the
- Spiral between Rijeka-Brajdica and Sušak-Pećine at on the Rijeka–Karlovac railway, part of International corridor V. The spiral is mainly in a 1838m long tunnel.
- Three spirals on the Col de Tende line between Ventimiglia to Cuneo as it passes through France, a further spiral on this line is in Italy.:155
- Spiral at Moûtiers at between Albertville and Bourg-Saint-Maurice used by TGV.
- There was a spiral railway in Sayerce tunnel between Pau and Zaragoza (Spain) in the Pyrenees. This spiral is now a footpath.
- The proposed four-turn spiral of Gravenne de Montpezat ( ) on the partly completed Ligne Transcévenole between Saint-Cirgues and Aubenas (Ardèche) in the Cévennes was never constructed.
- Spiral on the northern approach to the Rendsburg High Bridge in Rendsburg, Schleswig-Holstein at has a single spiral loop onto the transporter bridge crossing the Kiel Canal.:43
- Spiral on the Wutach Valley Railway at . The line was built partly for strategic reasons and had to be built to a reasonable gradient in order to haul heavy military trains over it. The alternative, shorter Singen–Waldshut route was not available for this traffic, since it crossed Swiss territory. The line is now a heritage railway.:58
- There are three spirals on the Darjeeling Himalayan Railway:
- (formerly) Spiral at Dhulghat at between Khandwa and Hingoli on the 1,000 mm (3 ft 3 3⁄8 in) gauge railway.:41
- The St. James's Gate Brewery, Dublin, Ireland formerly had an internal 1 ft 10 in (559 mm) gauge railway with a loop in a tunnel to gain height between buildings
- Spiral at Bortigiadas on the Sassari-Palau railway part of the Ferrovie della Sardegna.:179
- Spiral near Lanusei on the Mandas–Gairo–Arbatax railway part of the Ferrovie della Sardegna.:190
- Varzo spiral near Iselle di Trasquera on the Swiss Federal Railways just South of the Southern Portal of the Simplon Tunnel.:9
- Spiral near Vernante on the Col de Tende railway from Ventimiglia to Cuneo on the Ferrovie dello Stato Italiane. There are a further three spirals on this line in French territory.:60:155
- Spiral close to Savona at on the Savona–Altare line on the Ferrovie dello Stato Italiane.:62:155
- Spiral just North of Salerno at on the Salerno–Mercato San Severino railway on the Ferrovie dello Stato Italiane.:86:129:164
- Spiral at Ragusa at on the approach to Ragusa from Modica on the Ferrovie dello Stato Italiane.:177:168
- Spiral at Casole Bruzio on the Cosenza to San Giovanni in Fiore line (line is not in regular service).:87
- There were three spirals on the former Spoleto–Norcia line at Caprareccia and San Martino.
- Spiral South of Echigo-Nakazato at on the Tokyo bound Jōetsu Line.:53
- Spiral at Yubiso at on the Tokyo-bound Jōetsu Line.:53
- Spiral South of Tsuruga Station at on the Hokuriku Main Line to Shin-Hikida Station, track for Maibara Station only.:73
- Spiral at Okoba Station at on the Hisatsu Line. Okoba Station is situated on a zig zag part way around the loop.:131
- Spiral on the Nakamura Line just after its junction with the Yodo Line at .:122
- Spiral on the western approach to the Rainbow Bridge at on New Transit Yurikamome automated transit service in Tokyo.:149
- Three spirals on the Kenya to Uganda Railway Line, a fourth spiral on this line is in Uganda.
- Spiral at Geumdae 2nd Tunnel at Jungang Line;– one loop, single track. New double track tunnel is under construction to replace loop tunnel. between Geumgyo station and Chiak station on
- Spiral at Daegang Tunnel at Jungang Line;– one loop, single track. between Danseong station and Jungnyeong station on the
- Spiral at Hambaek 1st Tunnel at Hambaek Line;– one loop, single track. between Hambaek station and Jodong station on the
- Spiral at Solan Tunnel at Yeongdong Line;– one loop, single track but double track is installed on the middle of the tunnel; for both trains crossing each other. between East Baeksan station and Dogye station on the
- Two spirals on the Burmah Mines Railway
- One spiral close to Schwenyaung at on the Thazi-Schwenyuang line.
- Raurimu Spiral at on the North Island Main Trunk. The line is single track and involves two short tunnels around a suitable hill.
- Spiral on the Driving Creek Railway at . This railway also has several reverses or zig-zags.
- There was formerly a spiral on the Ellis & Burnand Ongarue tramway which closed in 1958 and is now a cycle trail.
- Spiral at Jatare at on the Šargan Eight Heritage Railway in Western Serbia between from Mokra Gora and Šargan Vitasi.
- Spiral at Telgártska slučka at on the Brezno to Gelnica Line. The spiral is constructed of two viaducts and a 1,200m tunnel.
- Spiral near Komga at on the branch line to Mthatha as it descends to the Great Kei River.
- Spiral at Van Reenen's Pass at on the line from Harrismith to Ladysmith.
- Spiral near Toses at on the Ripoll to Latour-de-Carol, France line.:30
- Spiral at La Granja de San Vicente at on the Palencia to A Coruña line.:18
- Spiral at Demodara railway station at on the line from Bandarawela to Badulla. Demodara railway station is located above the spiral tunnel.
- The Gotthard railway has spirals and horseshoe curves or bends mostly in tunnels on its standard gauge, double track line.:143 The spirals are:
- RhB Albulabahn has four spirals, mainly in tunnels, on its metre gauge single track.:144 The spirals are at:
- Spiral at Brusio at on RhB Berninabahn. This is a fine example of an open spiral mainly on the Brusio spiral viaduct on a metre gauge single track railway.:145
- Spiral South of Gletsch at on the former Furka Oberalp Bahn, now Dampfbahn Furka-Bergstrecke Heritage Railway. This is a single track, metre gauge rack railway with the catenary equipment removed.
- Spiral East of Grengiols at on the former Furka Oberalp Bahn, now Matterhorn Gotthard Bahn, between Grengiols and Lax.:148
- Spiral at Circle Hill Kenya to Uganda Railway Line in Kamwenge District, Western Uganda. There are three spirals on this railway in Kenya. on the
- Spiral around Dduallt railway station at on the 1 ft 11½ in (597 mm) gauge Ffestiniog Railway in Wales.
- The line at Coombe Junction and Liskeard on the Looe Valley Line and on over Moorswater Viaduct forms a complete spiral, climbing up to join the main line at Liskeard. Not all parts are used by passenger trains. from Moorswater cement terminal, through
- Tehachapi Loop, at Tehachapi, California at on the former Southern Pacific Railroad, now part of Union Pacific Railroad.
- Williams Loop, east of East Quincy, California at on the former Western Pacific Railroad now part of Union Pacific Railroad.
- Hiwassee Loop, 2 miles NNE of Farner, Tennessee at on the former Atlanta, Knoxville and Northern Railway now operated as a heritage site by the Tennessee Valley Railroad Museum.
- Georgetown Loop, at Georgetown, Colorado at on the former Colorado Central Railroad. The spiral was completed in 1884, abandoned and dismantled in 1939, rebuilt between 1972 and 1984 and is now owned by History Colorado and operated as the Georgetown Loop Railroad.
- Riflesight Notch Loop (track dismantled) at Rollinsville, Colorado on the former Denver and Salt Lake Railway. The spiral was bypassed by the Moffat Tunnel, built in 1928. The spiral was abandoned and the track was dismantled in 1935.
- Double Circle, a.k.a. Double Loop, or The Golden Circle, east of Eureka, Utah on the former Denver and Rio Grande Western Railroad. It was bypassed in 1940 and subsequently dismantled.   
- There used to be spiral on the Roaring Camp Railroad at . The spiral was completed in 1963. The spiral was bypassed by two switchbacks after a trestle fire in 1976. 
- Spiral bridge - road equivalent
- Hairpin turn
- Horseshoe curve
- List of spiral tunnels and tunnels on a curved alignment
- List of steepest gradients on adhesion railways
- Zig Zag Railways
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