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. 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.

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.

Alternate names

* In the United States, zig zags are called switchbacks.

Location of zig zags

* Argentina
** Tren a las Nubes
* Australia
** Kalamunda Zig Zag - 2 reversals
** Lapstone Zig Zag - 2 reversals
** Lithgow Zig Zag ( see Zig Zag Railway )
** Mundaring Weir Branch Railway
** out of use
*** Jarrahglen (dismantled)
*** Yarloop (dismantled)
*China
**Qinglongqiao on the Jingbao Railway
* France
** Froissy Dompierre Light Railway
*Germany
**Zig Zags in use
*** Rauenstein (railway-line: Hinterlandbahn)
*** Lauscha (railway-line: Sonneberg – Probstzella)
*** Ernstthal am Rennsteig: created by close of the railway-line: Ernstthal–Probstzella
*** Rennsteig (railway-line: Rennsteigbahn, Ilmenau – Themar)
*** Michaelstein (railway-line: Rübelandbahn)
*** Wurzbach (railway-line: Saalfeld – Blankenstein)
** out of use
*** Schillingsfürst (dismantled)
*** Lenzkirch in the Blackforrest (dismantled)
*** Elm (replaced in 1914 by Distelrasen-Tunnel, but the structure is conserved within the railway-lines Frankfurt am Main - Fulda, Fulda - Gemünden and the connecting curve between the stations Elm and Schlüchtern
*** Railway-line Steinhelle-Medebach (double zig zag)
*** Railwaystation "Mainspitze" in Frankfurt am Main, used from 1846 - 1848 to reach the provisional Frankfurt terminal of the Main-Neckar-Eisenbahn (dismantled)
*** Erdbach-Station, Westerwaldquerbahn
* 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
* Japan
** Hakone Tozan Line has three zig zags, namely at Deyama S.B., hiradai Station, Kami-Ōhidradai S.B.
** Hhi 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 2009 and will be replaced by new tunnel .
* Pakistan
** Khyber Pass
* Peru
** Cacray Zigzag on the Central Railway of Peru - with 9 switchbacks
** PeruRail between Cuzco to Machu Picchu - 5 switchbacks
* Taiwan
**Alishan Forest Railway
* Burma (also known as Myanmar)
** Passenger line between Thazi and Kalaw, with 4 switchbacks, still in use
* United States
** 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
* Mount Hood Railroad, Hood River, Oregon - One switchback, still in use