Zig zag (railway)

A railway zig zag, also called a switchback, is a way of climbing hills in difficult country with a minimal need for tunnels and heavy earthworks.^[1] For a short distance (corresponding to the middle leg of the letter "Z"), the direction of travel is reversed, before the original direction is resumed.^[2]

A location on railways constructed e.g. to ascend very steep gradients by using a zig-zag alignment at which trains have to reverse direction in order to continue is a reversing station.^[3]

Advantages

The advantages of a zig zag include speed and relative cheapness of construction, with no need to worsen the ruling grade, compared to the alternative which almost certainly will require tunnels which are slow and costly to build. Where traffic is modest, a zig zag may well be a sensible long term solution.

Disadvantages

Zig zags suffer from a number of possible limitations:

• The length of a train will be limited by length of track at the top and bottom points.
• Reversing a train without running an engine around to the rear of the train is hazardous. Top and tail or push pull operation with engines at the rear of the train helps.
• The process is slow.

Location of zig zags

• Argentina
  • Tren a las Nubes (1921)
• Australia
  • Lithgow Zig Zag ( see Zig Zag Railway ) (1869)
  • out of use
    • Jarrahglen (dismantled)
    • Kalamunda Zig Zag - 2 reversals
    • Lapstone Zig Zag - 2 reversals (1865)
    • Mundaring Weir Branch Railway
    • Yarloop, Western Australia (dismantled)
    • Lake Margaret Tram 610 mm (2 ft) 
• China
  • Qinglongqiao on the Jingbao Railway
• Chile
  • Pisagua - 3 reversals; long out of use but earthworks easy to trace.
• Denmark
  • Lemvig - Small side track from the harbor to the railway station, used only on special occasions. In reality only half a 'Z' as only one reversal is needed.
• Ecuador
  • Sibambe on the Quito-Guayaquil line (cf. Empresa de Ferrocarriles Ecuatorianos)
• France
  • Froissy Dompierre Light Railway
• Germany
  • Zig Zags in use
    • Rauenstein (Hinterland Railway)
    • Lauscha (Sonneberg – Probstzella railway)
    • Ernstthal am Rennsteig: created by close of the Ernstthal–Probstzella railway
    • Railway serving the island of Nordstrandischmoor off the coast in the North Sea
    • Rennsteig (Rennsteig Railway, Ilmenau – Themar)
    • Michaelstein (Rübeland Railway)
    • Wurzbach (Saalfeld – Blankenstein railway)
  • out of use
    • Schillingsfürst (dismantled)
    • Lenzkirch in the Black Forest (dismantled)
    • Elm (replaced in 1914 by Distelrasen Tunnel, but the structure is conserved within the Frankfurt am Main - Fulda and Fulda - Gemünden railways and the connecting curve between the stations at Elm and Schlüchtern
    • Steinhelle-Medebach railway (double zig zag)
    • Mainspitzestation in Frankfurt am Main, used from 1846 - 1848 to reach the provisional Frankfurt terminal of the Main-Neckar Railway (dismantled)
    • Erdbach station, Westerwald Railway
• Hungary
  • Nagybörzsönyi Erdei Vasút has a simple zig zag at the middle of the railway line between Kisirtás and Tolmács-hegy stations, with a loop in the middle of the Z shape, narrow gauge
• India
  • Darjeeling Himalayan Railway has six full zig zags, most are from the construction of the current railway but one was added in the 1940s and at least one other was used temporarily following storm damage, narrow gauge
  • Batasia Loop in Darjeeling Himalayan Railway
• Japan
  • Hakone Tozan Line has three zig zags, namely at Deyama S.B., Ōhiradai Station, Kami-Ōhidradai S.B.
  • Hōhi Main Line at Tateno Station
  • Kisuki Line at Izumo-Sakane Station
  • Hisatsu Line at Okoba and Masaki stations
  • Tateyama Sabō Erosion Control Works Service Train, the work train for an erosion control construction, is not open to general public, but deserves a mention for its 38 zig zags, 18 of them in a row.
  • Niyama Station on Hakodate Main Line (see #Wartime type switchback)
• South Korea
  • Yeongdong Line, between Heungjeon station and Nahanjeong station. This section will be closed in 2012 and will be replaced by new tunnel .
• Pakistan
  • Khyber Pass
• Peru
  • 7 full Zigzags and one single reverse on the Central Railway of Peru
  • PeruRail between Cuzco to Machu Picchu - 5 switchbacks
• Slovakia
  • Historical Logging Switchback Railway in Vychylovka
• Taiwan
  • Alishan Forest Railway
• Burma (also known as Myanmar)
  • Passenger line between Thazi and Kalaw, with 4 switchbacks, still in use
• United States
  • Hagans Switchback in Virginia
  • 8 Switchbacks at Cascade on GN - replaced by tunnel which was in turn replaced by a longer tunnel.
  • Cass Scenic Railroad, West Virginia - 2 switchbacks with 11% grade between, still in use
  • Confusion Hill Mountain Train Ride, Piercy, California - Several switchbacks in use.
  • Industrial switchback, Montage Mountain Road, Scranton, Pennsylvania - still in use
  • Mount Hood Railroad, Hood River, Oregon - One switchback, still in use
  • Roaring Camp and Big Trees Narrow Gauge Railroad, Felton, California - One switchback, still in use
  • Shasta Sunset Dinner Train, McCloud, California - One switchback, "Signal Butte Switchback", in use.

References

1. ^ Raymond, William G. (1912). "Railway Engineering". In Beach, Frederick Converse (Google books). The Americana: A Universal Reference Library, Comprising the Arts and Sciences, Literature, History, Biography, Geography, Commerce, Etc., of the World. 17. New York: Scientific American Compiling Department. http://books.google.com/books?id=Q6BPAAAAMAAJ. Retrieved 2010-01-03. "High mountain levels … may be tunneled … but … may be reached by one of several methods adopted to secure practical grades: (1) Zig-zag development … (2) Switchback development … (3) Spirals or loops …" 
2. ^ Raymond 1912. "Switch-back development … necessitating the use of switches at these ends and the backing of the train up alternate stretches."
3. ^ Jackson, Alan A. (2006). The Railway Dictionary, 4th ed., Sutton Publishing, Stroud, p. 285. ISBN 0-7509-4218-5.