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]
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.
Zig zags suffer from a number of limitations:
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. [7]
A hairpin turn is a bend in a road with a very acute inner angle, making it necessary for an oncoming vehicle to turn about 180° to continue on the road. It is named for its resemblance to a bent metal hairpin. Such turns in ramps and trails may be called switchbacks in American English, by analogy with switchback railways.
A spiral is a technique employed by railways to ascend steep hills.
The Zig Zag Railway is an Australian heritage railway, situated near Lithgow, New South Wales. It was opened by the not-for-profit Zig Zag Railway Co-op as an unpaid volunteer-staffed heritage railway in October 1975, using the alignment of the Lithgow Zig Zag line that formed part of the Main Western line between 1869 and 1910. The line climbs the western flank of the Blue Mountains, using railway zig zags to gain height.
Hillclimbing is a problem faced by railway systems when a load must be carried up an incline. While railways have a great ability to haul very heavy loads, this advantage is only significant when the tracks are fairly level. As soon as the gradients increase, the tonnage that can be hauled is greatly diminished.
A horseshoe curve is a class of climbing curve in a roadbed that reverses turn direction (inflection) twice on either side of a single tight curve that varies through an angle of about 180 degrees or more.
A gravity railroad or gravity railway is a railroad on a slope that allows cars carrying minerals or passengers to coast down the slope by the force of gravity alone. The speed of the cars is controlled by a braking mechanism on one or more cars on the train. The cars are then hauled back up the slope using animal power, a locomotive or a stationary engine and a cable, a chain or one or more wide, flat iron bands. A much later example in California used 4 ft 8+1⁄2 instandard gauge steam engines to pull gravity cars back to the summit of Mt. Tamalpais.
A double-track railway usually involves running one track in each direction, compared to a single-track railway where trains in both directions share the same track.
Lapstone is a township on the eastern escarpment of the Blue Mountains in New South Wales, Australia. Elevation 160 m (525 ft). Lapstone is located 62 kilometres west of the Sydney CBD in the local government area of the City of Blue Mountains and is part of the federal electorate of Macquarie. Lapstone consists mostly of stand-alone housing and has a few public facilities. At the 2016 census, Lapstone had a population of 961 people. Lapstone was originally bought and developed by Mr Arthur J Hand, an Alderman of the Blue Mountains City Council.
The Lapstone Zig Zag was a zig zag railway built between Emu Plains and Blaxland stations on the Main Western Line of New South Wales in Australia. Constructed between 1863 and 1865 to overcome an otherwise insurmountable climb up the eastern side of the Blue Mountains, the zig zag and associated Knapsack Viaduct, a sandstone arch viaduct, were designed by John Whitton, Engineer-in-Charge of New South Wales Government Railways, and were built by William Watkins. The zig zag was listed on the Blue Mountains local government heritage register on 27 December 1991; while the adjacent Knapsack Viaduct was listed on the New South Wales Heritage Database on 2 April 1999. The Lapstone Zig Zag was the world-first Zig Zag constructed on any main-line railway.
The Blue Mountains Line (BMT) is an intercity rail service serving the Blue Mountains region of New South Wales, Australia. The line travels west from Sydney to the major town of Katoomba and on to Mount Victoria, Lithgow and Bathurst. Mount Victoria is the terminus for most electric services, but some services terminate at Lithgow instead. Two express services per day in each direction, known as the Bathurst Bullet, extend to the regional city of Bathurst, which is supplemented by road coaches connecting Bathurst to Lithgow. Due to electrification limits at Lithgow, the Bathurst Bullet is run using the Endeavour railcars, which operate on diesel. The Blue Mountains Line operates over a mostly duplicated section of the Main Western line. As such, the tracks are also traversed by the Central West XPT, Outback Xplorer and Indian Pacific passenger services and by freight trains.
Zig Zag railway station is located on the New South Wales Main Western Line. It was originally built in April 1878 and closed in 1910 due to the opening of the Ten Tunnels Deviation which bypassed the original site of the station. The station was not rebuilt until 1959 when a new station was built alongside the 1910 alignment in a similar location to the 1878 station.
The Gilmore and Pittsburgh Railroad (G&P), now defunct, was an American railroad located in southwestern Montana and east-central Idaho. Constructed in 1909 and 1910 between Armstead, Montana, and Salmon, Idaho, the G&P served mining and agricultural areas in Lemhi County, Idaho, and Beaverhead County, Montana. The line was financially backed by the Northern Pacific Railway (NP) and later became its subsidiary. Never financially successful, the G&P ceased operations in 1939, and the railroad was dismantled the following year.
The Main Western Railway is a major railway in New South Wales, Australia. It runs through the Blue Mountains, and Central West regions. It is 825 kilometres (513 mi) long, of which 484 kilometres (301 mi) is currently operational.
The Lithgow Zig Zag is a heritage-listed former zig zag railway line built near Lithgow on the Great Western Line of New South Wales in Australia. The zig zag line operated between 1869 and 1910, to overcome an otherwise insurmountable climb and descent on the western side of the Blue Mountains. It was designed by John Whitton and built from 1863 to 1869 by Patrick Higgins as contractor. It is also known as the Great Zig Zag Railway and Reserves and Zig Zag Railway. The property is owned by Department of Planning and Infrastructure. It was added to the New South Wales State Heritage Register on 2 April 1999.
The Ten Tunnels Deviation is a heritage-listed 9.2-kilometre (5.7 mi) section of the Main Western Line between Newnes Junction and Zig Zag stations in Lithgow, New South Wales, Australia. It was designed and built by the New South Wales Government Railways and built from 1 June 1908 and 16 October 1910. It is also known as Great Zig Zag Railway deviation tunnels and Bell to Zig Zag Ten Tunnel Railway Deviation. It was added to the New South Wales State Heritage Register on 2 April 1999.
The Neudietendorf–Ritschenhausen railway connects Neudietendorf and Ritschenhausen in the German state of Thuringia. It is a mainly single-track main line operated by DB Netze.
Flieden station is a station in the town of Flieden in the German state of Hesse, where the Flieden–Gemünden railway branches off the Frankfurt–Göttingen railway. The station is classified by Deutsche Bahn (DB) as a category 5 station.
The Simplon Railway is a line that links Lausanne in Switzerland and Domodossola in Italy, via Brig. The 20 km (12 mi)-long Simplon Tunnel is a major part of it. The line between Lausanne and Vallorbe is sometimes considered to form part of the line, making it 233 km (145 mi) long.
Bottom Points is a railway station on the Zig Zag Railway in the Blue Mountains area of New South Wales.
The Glenbrook Tunnel is a heritage-listed single-track former railway tunnel and mustard gas storage facility and previously a mushroom farm located on the former Main Western Line at the Great Western Highway, Glenbrook, in the City of Blue Mountains local government area of New South Wales, Australia. The Department of Railways designed the tunnel and built it from 1891 to 1892. It is also known as Lapstone Hill tunnel and Former Glenbrook Railway and World War II Mustard Gas Storage Tunnel. The property is owned by Blue Mountains City Council and Land and Property Management Authority, an agency of the Government of New South Wales. It was added to the New South Wales State Heritage Register on 5 August 2011. The railway tunnel was originally part of the Glenbrook 1892 single-track deviation, which bypassed the Lapstone Zig Zag across the Blue Mountains. It is 634 metres; 693 yards long and is constructed in an 'S' shape with a gradient of 1:33.
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 …