Zig zag (railway) explained
A railway zig zag or switchback is a railway operation in which a train is required to switch its direction of travel in order to continue its journey. While this may be required purely from an operations standpoint, it is also ideal for climbing steep gradients with 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] Some switchbacks do not come in pairs, and the train may then need to travel backwards for a considerable distance.
A location on railways constructed by using a zig-zag alignment at which trains must reverse direction to continue is a reversing station.[3]
One of the best examples is the Darjeeling Himalayan Railway, a UNESCO World Heritage Site railway in India, which has six full zig zags and three spirals.[4]
Advantages
Zig zags tend to be cheaper to construct because the grades required are discontinuous. Civil engineers can generally find a series of shorter segments going back and forth up the side of a hill more easily and with less grading than they can a continuous grade, which must contend with the larger scale geography of the hills to be surmounted.
Disadvantages
Zig zags suffer from a number of limitations:
- The length of trains is limited to what will fit on the shortest stub track in the zig zag. For this reason, the Lithgow Zig Zag's stubs were extended at great expense in 1908.[5] Even then, delays were such that the zig zag had eventually to be bypassed by a new route, opened two years later.
- Reversing a locomotive-hauled train not purposely equipped for push-pull operation without first running the engine around to the rear of the train can be hazardous – although operating the train with two locomotives, one at each end (a practice known as "topping-and-tailing"), can mitigate the dangers.
- The need to stop the train after each segment, throw the switch, and then reverse means that progress through the zig zag is slow.
- Passenger cars with transverse seating force riders to travel in reverse for at least part of the journey, though this issue is largely solved by longitudinal seating on cars serving such routes.
Hazards
If the wagons in a freight train are marshaled poorly, with a light vehicle located between heavier ones (particularly with buffer couplings), the move on the middle road of a zig zag can cause derailment of the light wagon.[6]
Examples
- Argentina
- Australia
- Chile
- Pisagua – Three reversals; long out of use but earthworks easy to trace
- China
- Czech Republic
- Dubí - local railway between Moldava and Most (Most–Moldava railway), trains have to change direction in station Dubí in order to continue further. Only one halt of a 'Z' is placed
- 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
- France
- Germany
- Hungary
- The Szob-Nagybörzsöny forest railway 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
- India
- Darjeeling Himalayan Railway has six full zig zags and 3 spirals, 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
- Matheran_Hill_Railway has three zig zags
- Indonesia
- Jalur kereta api Cikampek–Padalarang Dutch East Indies made this line to shorten the travel time between the two biggest cities Jakarta and Bandung
- Italy
- Japan
- Mexico
- Ferrocarril Noroeste de México, between Juan Mata Ortiz to Chico
- Myanmar
- Passenger line between Thazi and Kalaw, with four switchbacks; still in use
- Passenger line between Mandalay and Lashio
- New Zealand
- North Korea
- Kanggye Line, between Hwangp'o and Simrip'yŏng stations
- Kŭmgangsan Electric Railway, between Tanballyŏng and Malhwiri (Kŭmganggu) stations. Entire line destroyed during the Korean War and not rebuilt
- Paengmu Line, between Yugok and Rajŏk stations, and at Samyu station (station is located on a single reverse)
- in addition, there are numerous switchbacks on spurs into underground facilities located off main lines.
- Pakistan
- Peru
- Slovakia
- South Africa
- Tierkrans Switchback Railway, between Barkley East station and Aliwal-North station. For economic reasons regular service was finally discontinued in 1991. Railway enthusiasts also know the line for the famous set of eight reverses.
- South Korea
- Yeongdong Line, between Heungjeon station and Nahanjeong station. This section closed in 2012 and replaced by Solan tunnel
- Sweden
- Lövsjöväxeln (Lövsjö points) on Hällefors-Fredriksbergs Järnvägar (1875–1940)[8]
- Visby harbour från Visby station, 32 meters of difference, (1868–1962),[9]
- Switzerland
- Taiwan
- United Kingdom
- United States
- Buckingham Branch Railroad, New Canton, Virginia – One switchback at New Canton
- Eight switchbacks at Cascade on GN – Replaced by tunnel which was in turn replaced by a longer tunnel
- Cass Scenic Railroad, West Virginia – Two switchbacks with 11% grade between, still in use
- Colorado and Southern Railway, Central City, Colorado – Two switchbacks on the ascent from Black Hawk, Colorado to Central City
- Confusion Hill Mountain Train Ride, Piercy, California – Several switchbacks in use
- Crown King Branch, Bradshaw Mountain Railroad, Yavapai County, Arizona - 10 switchbacks were utilized on the line between Mayer, Arizona and Crown King, Arizona.
- Fern Rock Transportation Center, Fern Rock, Philadelphia - One switchback, connects the Broad Street Line with SEPTA Regional Rail, still in limited use
- Hagans Switchback in Virginia, Still in use by CSX for Coal trains
- Industrial switchback, Montage Mountain Road, Scranton, Pennsylvania – Still in use
- Market Street Railway 33 18th and Park streetcar, San Francisco, California – One switchback, route converted to trolleybus but still largely following original alignment with a very sharp turn at the former switchback[10]
- Monarch Branch, Denver and Rio Grande Western Railroad, Colorado – Two switchbacks
- Mount Hood Railroad, Hood River, Oregon – One switchback, still in use
- Northern Pacific's Coeur d'Alene Branch, Lookout Pass – One switchback east of Mullan, Idaho along its 4% descent towards Wallace
- Roaring Camp and Big Trees Narrow Gauge Railroad, Felton, California – One switchback bypassing a spiral trestle destroyed by fire in 1976; still in use
- Shasta Sunset Dinner Train, McCloud, California – One switchback, "Signal Butte Switchback", line out of service since 2010
- Sierra Railway, Melones, California - Two switchbacks, abandoned, used by SRY's Angels Branch to cross Stanislaus River Canyon, one switchback inundated by New Melones Lake
Notes and References
- Encyclopedia: Raymond. William G.. Beach, Frederick Converse. The Americana: A Universal Reference Library, Comprising the Arts and Sciences, Literature, History, Biography, Geography, Commerce, Etc., of the World. Railway Engineering. Google books. 3 January 2010. 1912. Scientific American Compiling Department. 17. New York. 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 ….
- Raymond 1912. "Switch-back development … necessitating the use of switches at these ends and the backing of the train up alternate stretches."
- Book: Jackson, Alan A.. 2006. The Railway Dictionary. 4th. Sutton Publishing. Stroud. 285. 0-7509-4218-5.
- Web site: UNESCO World Heritage Centre. Mountain Railways of India. 2006-04-30.
- News: The Zig-Zag Deviation. . . NSW . 5 December 1908 . 17 February 2013 . 4 . National Library of Australia.
- News: The Railway Accident on the Zig-zag. . . NSW . 10 April 1895 . 19 February 2013 . 3 . National Library of Australia.
- Web site: Historical and Archaeological Assessment of Proposed Cycleway, Near Thornleigh Quarry, Via De Saxe Close, Thornleigh (Berowra Valley Regional Park), N.S.W.. The construction of the railway siding and zig-zag to the quarry and also Hall’s Camp were associated with Amos & Co, who won the contract to build the section of railway from Strathfield to Hawkesbury River.. Edward Higginbotham & Associates PTY LTD. March 2002. 19 November 2017.
- Web site: Bang rdsskisser SVJ/HFJ. www.ekeving.se.
- Web site: Bandel 660. www.historiskt.nu. 2020-11-19.
- Book: Vielbaum . Walt . Hoffman . Philip . Ute . Grant . Townley . Robert . San Francisco's Market Street Railway . 2005 . . 9780738529677 . 86–87.
