A railwayzig 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]
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.
Railwaystation Mainspitze in Frankfurt am Main, used from 1846 - 1848 to reach the provisional Frankfurt terminal of the [[Main-Neckar-Eisenbahn] (dismantled)
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
Tateyama Sab? 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.
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