Spiral (railway)

For the engineering term applying to railway track geometry, see Track transition curve.

Spiral viaduct near Brusio, Switzerland.

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 of sufficient length, it is often possible to view the train looping above itself.

A spiral loop should not be confused with 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. These curve layouts are also used in highway engineering.

Spirals are not generally needed on tramways (street running or reserved track) or light rail lines because trams traditionally have all wheels powered, giving the ability to climb much steeper direct gradients than railways. In addition, the space consumed by a spiral is usually not available in an urban environment.

A similar feature to railway spirals in road design is the pigtail bridge.

Calculations

On a railway climbing at a gradient of 1 in 40 (2.5%, or 25 m per km) a 360-degree spiral at 350 m radius will add 2200 m to the forward journey and 55 m to the vertical climb. Unless the topography has a suitably shaped hill, the spiral is likely to include a tunnel, increasing construction costs and creating problems if steam locomotives are employed. If a convenient side valley is available, then a horseshoe curve may be possible.

The spiral needs to climb about 6 m in order to bridge itself. With steam locomotives and to a lesser extent with diesel locomotives, the gradient in any long tunnel(s) should be less than the ruling grade to avoid problems with fumes and dampness causing the driving wheels to slip.

List of spirals

See also: Table of turn tunnels

This list is incomplete; you can help by expanding it.

Argentina

• 2 spirals south of Diego de Almagro station on theTren a las Nubes line

Australia

• Bethungra Spiral two very short tunnels, uphill track in spiral at 1 in 66 gradient, downhill track plain at 1 in 40 gradient
• Cougal Spiral one short and one long tunnel, single track

Austria

• An early spiral on the Brenner Railway is apparently called a winding.

Bolivia

• Spiral south of Zudáñez on closed railway line starting at Taburoco

Bulgaria

• 4 spirals at Septemvri – Dobrinishte railway 760 mm (2 ft 5 ¹⁵⁄₁₆ in) gauge.
• Klisura – 3rd main railway line, the spiral is built around the town
• 2 spirals at Radevtsi and Raduntsi on 4th mainline.

Canada

• Spiral tunnels between Field, BC, and the summit of Kicking Horse Pass, Canadian Pacific Railway.
• Trinity Loop near Trinity, Newfoundland
  • The Newfoundland Railway no longer exists
• Rogers Pass

Chile

• Transandine Railway connecting Chile and Argentina

People's Republic of China

• Yangjiawan – Qinling Tunnel
• On the Chengdu-Kunming Railway, there is a spiral north of Heijing Town

Croatia

• Tunnel 1838 m long (0+525 – 2+363) between Rijeka-Brajdica and Sušak-Pećine stations on the southern approach to the Rijeka–Karlovac railway, part of International corridor V.

France

• Sayerce tunnel between Pau and Zaragossa (Spain) in the Pyrenees
• Nice–Cuneo (Italy), three spirals.
• Moûtiers, between Albertville and Bourg-Saint-Maurice (Savoie), () used by TGV.
• 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.

Germany

• The northern approach to the Rendsburg High Bridge in Rendsburg, Schleswig-Holstein has a unique oblong single loop onto the transporter bridge crossing the Kiel Canal
• The Wutach Valley Railway had to be built less steep than possible to haul heavy military trains over it, since it bypassed for the shorter Singen–Waldshut route crossing Swiss territory.

India

Loop (Agony Point) on the DHR, India

• Darjeeling Himalayan Railway (DHR) has three (originally five) loops, of which one is a double spiral. 2 ft (610 mm) gauge
• Dhulghat Spiral Between Khandwa and Hingoli, 1,000 mm (3 ft 3 ³⁄₈ in) metre gauge

Iran

• Numerous spirals through very mountainous regions, mostly entirely in tunnel and single track, e.g. the Three Golden Lines.

Ireland

• The St. James's Gate Brewery, Dublin, Ireland had an internal 1 ft 10 in (559 mm) gauge railway with a loop in a tunnel to gain height between buildings

Italy

• At Sassari-Palau railway on the Ferrovie della Sardegna.
• At Mandas–Gairo–Arbatax railway close to Lanusei railway station on the Ferrovie della Sardegna.
• At Iselle di Trasquera on the Swiss Federal Railways.
• At Vernante on the FS.
• Close to Savona on the Savona–Altare line on the FS.
• At Caprareccia and San Martino on the Spoleto–Norcia line there were in total three spirals.
• At Salerno on the Salerno–Mercato San Severino line.
• At Casole Bruzio on the Cosenza–San Giovanni in Fiore line.
• At Ragusa on the FS.
• At Varzo on the Italian approaches to the Simplon tunnel.

Japan

File:Okoba spiral and zig zag aerial photography 1976-001.jpg

Okoba spiral and Zig zag in Hisatsu Line, Japan

• Jōetsu Line has two spirals, track towards Tokyo only
• Hokuriku Main Line from Tsuruga Station to Shin-Hikida Station, track for Maibara Station only
• Hisatsu Line between Yatake Station and Okoba Station, with a zig zag in the loop
• Tosa Kuroshio Railway Nakamura Line between Kawaoku S.B. and Kaina Station
• Yurikamome, western approach to the Rainbow Bridge

Kenya

• Kenya–Uganda four spirals on the Kenya to Uganda line.

Mazeras Spiral near Mombasa, at: -3.995257° 39.546742° (map)
Spiral near Makutano station, at: -0.043457° 35.641461°
Spiral near Equator, Kenya station, at: -0.007183° 35.551033°

South Korea

Geumdae 2nd Tunnel in Jungang Line, South Korea

• Geumdae 2nd Tunnel – between Geumgyo station and Chiak station on Jungang Line – one loop, single track. New double track tunnel is under construction to replace loop tunnel.
• Daegang Tunnel – between Danseong station and Jungnyeong station on the Jungang Line – one loop, single track.
• Hambaek 1st Tunnel – between Hambaek station and Jodong station on the Hambaek Line – one loop, single track.
• Solan Tunnel – between East Baeksan station and Dogye station on the Yeongdong Line – one loop, single track but double track is installed on the middle of the tunnel; for both trains crossing each other. It will be opened in 2012.

Madagascar

• One loop at Anjiro on the main line from Antananarivo to Toamasina.

Myanmar

Spiral in Thazi – Taunggyi line, Myanmar

• Two spirals on the Burmah Mines Railway
• One spiral close to Schwenyaung on the Thazi-Schwenyuang line

New Zealand

• Raurimu Spiral on the North Island Main Trunk, single track, suitable hill, two short tunnels. See Map and Photo.
• Driving Creek Railway
• Ellis & Burnand Ongarue tramway (closed 1958, now a cycle trail).

Norway

• Flåm Line: between Myrdal and Flåm – tunnels that spiral in and out of the mountainside.
• Rauma Line: near the Kylling Bridge

Russia

• Bolshoy Petlevoy, Sredniy Petlevoy and Maly Petlevoy Tunnels (Major, Middle and Minor Loop Tunnels) – 3 tunnels on a single loop of North Caucasus Railway ()

Serbia

• Šarganska osmica in Western Serbia, from Mokra Gora to Šargan Vitasi.

Slovakia

• Telgárt Loop (Telgártska slučka – Slovak language), consists of 2 viaducts and 1,2 km tunnel.

South Africa

• There is a spiral on the descent to the Great Kei River on the branch line to Mthatha.
• At the Zand River crossing on the Bloemfontein to Kroonstad line the high-level bridge was destroyed by fighting in the second Boer War. Spiral tracks were constructed by military engineers to access a temporary bridge at river level.
• The rail line at Van Reenen's Pass has a spiral tunnel.

Spain

• Cargol Tunnel on the Ripoll – La Tour de Carol (France) line
• El Lazo Tunnel on the Palencia – La Coruña line

Sri Lanka

• Demodera

Switzerland

File:Albulabahn01.jpg

Toua spiral tunnel on the RhB Albulabahn

• Gotthardbahn has five spirals (and two turns), entirely in tunnel, double track, standard gauge
• RhB Albulabahn has four spirals (in tunnels), single track, metre gauge
• RhB Berninabahn has an open spiral mainly on the Brusio spiral viaduct (near Brusio), single track, metre gauge
• Former Furka-Oberalp-Bahn, now Dampfbahn Furka-Bergstrecke heritage railway, has one spiral tunnel, single track, cog rail, metre gauge, catenary removed
• Former Furka-Oberalp-Bahn, now Matterhorn-Gotthard-Bahn, between Grengiols and Lax, single track, metre gauge, cog rail, entirely in tunnel

Taiwan

• Alishan Forest Railway

Uganda

See Kenya above.

United Kingdom

File:Dduallt spiral simkins.jpg

The bridge on the spiral loop at Dduallt on the Ffestiniog Railway, Wales.

• Dduallt Loop, Ffestiniog Railway in Wales, 1 ft 11½ in (597 mm) gauge
• The line from Moorswater cement terminal, through 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.

United States

File:Tehachapi Loop USGS closeup.jpg

Tehachapi Loop, on the Union Pacific Railroad, California, US, viewed from the air.

1903 view of Riflesight Notch loop, near Rollins Pass in Colorado

• Hiwassee Loop - Farner, Tennessee - Marietta and North Georgia Railroad/Marietta and North Georgia Railway/Atlanta, Knoxville and Northern Railway/Louisville and Nashville Railroad/SCL-L&N Family Lines/Seaboard System Railroad/CSX Transportation - track wraps around a hill twice and crosses over itself on an 80-foot-tall (24 m) trestle - In service by Tennessee Valley Railroad Museum
• Georgetown Loop - Georgetown, Colorado - Colorado Central/Georgetown, Breckenridge, and Leadville/Union Pacific, Denver, and Gulf/Colorado and Southern - completed 1884, abandoned and dismantled 1939, rebuilt 1972-84 - owned by Colorado historical Society and operated as Georgetown Loop Railroad
• The "Golden Circle"/Homasville Loop/"Double Circle" Loop - Eureka, Utah – Tintic Range Railway/Rio Grande Western Railroad/Denver and Rio Grande Western - bypassed in 1940, abandoned, dismantled
• Riflesight Notch Loop - Rollinsville, Colorado - Denver Northwestern and Pacific/Denver and Salt Lake ("Moffat Road") - bypassed by Moffat Tunnel in 1928, abandoned and track dismantled 1935, trestle still partly standing
• Roaring Camp Loop – Felton, California - Roaring Camp and Big Trees Narrow Gauge Railroad (3 ft (914 mm) gauge) - Completed 1963, bypassed after 1976 trestle fire, trestles still partly standing, to be rebuilt
• Tehachapi Loop - Tehachapi, California (Walong) - Southern Pacific/Union Pacific - constructed 1872-76, in service as of 2015
• Williams Loop - Quincy, California (Spring Garden) - Western Pacific/Union Pacific - completed 1909, in service as of 2015

See also

• Hairpin turn
• Horseshoe curve
• Spiral tunnels and tunnels on a curved alignment

External links

• Helixes, Tunnels, Spirals, and Other Unique Trackage