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The size of tunnels dictates the maximum size of the trains.

A loading gauge is the envelope or contoured shape within which all railroad cars, locomotives, coaches, buses, trucks and other vehicles, must fit. Though often thought of as a height and width, it is in fact dictated by a number of dimensions and factors: the size of tunnels, height of bridges, the shape, height and position of third rail covers (if the third rail is covered at all) as well as the shape, height and position of railway platforms. Train stops and other signalling equipment must also be cleared, as must the rack of the rack railways. It varies between different countries and may also vary on different lines within a country. For example, metro trains might have smaller loading gauge than conventional trains to allow smaller tunnels. In that case metro trains may run on conventional tracks, but not vice versa. Image File history File links Emblem-important. ... Image File history File links Question_book-3. ... Image File history File links Acap. ... Image File history File links Why_London_Underground_is_nicknamed_The_Tube. ... Image File history File links Why_London_Underground_is_nicknamed_The_Tube. ... A railroad car (or, more briefly, car), also known as an item of rolling stock in British parlance, is a vehicle on a railroad or railway that is not a locomotive - one that provides another purpose than purely haulage, although some types of car are powered. ... Great Western Railway No. ... For other uses, see Coach. ... Autobus redirects here. ... For other uses, see Truck (disambiguation). ... The Trikke is a Human Powered Vehicle (HPV) Automobiles are among the most commonly used engine powered vehicles. ... A disused railway tunnel now converted to pedestrian and bicycle use, near Houyet, Belgium A tunnel is an underground passage. ... This article is about the edifice (including an index to articles on specific bridge types). ... Third rail at the West Falls Church Metro stop in Washington, D.C., electrified to 750 volts. ... A railway platform is a section of pathway, alongside rail tracks at a train station, metro station or tram stop, at which passengers may board or alight from trains or trams. ... Part of a railway signaling system, a train stop or trip stop (sometimes called a tripper) is a safety device that automatically stops a train if it attempts to pass a signal when the signal aspect and operating rules prohibit such movement, or if it attempts to pass at an... A signal is a mechanical or electrical device that indicates to train drivers or engineers information about the state of the line ahead, and therefore whether he or she must stop or may proceed, or instructions on what speed the train may go. ... Rack and pinion animation A rack and pinion is a pair of gears which convert rotational motion into linear motion. ... Rack railway track using Von Roll system rack. ... “Mass Transit” redirects here. ... For other uses, see Train (disambiguation). ...

In more recent times, the term loading gauge has fallen out of use among railway professionals, since it is a purely static concept and ignores other factors affecting clearance. Instead, the terms dynamic envelope or kinematic envelope are used. Factors such as suspension travel, overhang on curves (at both ends and middle), lateral motion on the track, etc. are just as important as the vehicle's static profile. All these factors must be considered in determining whether the moving rail vehicle will fit within allowed clearances.

Structure gauge vs. loading gauge

• loading gauge is maximum size of rolling stock,
• structure gauge is minimum size of bridges and tunnels,

The structure gauge must be larger than the loading gauge to allow for engineering tolerances and car motion. The difference between the two is called the clearance. The Structure gauge, also called the minimum clearance outline, is the minimum size of tunnels and bridges as well as the minimum size of the doors that allow a rail siding access into a warehouse. ... In engineering, tolerance is the permissible limit of variation in 1) a physical dimension, 2) a measured value or property of a material, manufactured object, system, or service, or 3) other measured values (such as temperature, humidity, etc). ... A clearance can refer to: a closeout sale in engineering and safety, a physical distance or space tolerance, as in a truck (lorry) or boat under a bridge an authorization or permission from an authority (i. ...

Loading gauges of the world

Different lines have different loading gauges. Tube lines on London Underground have the smallest loading gauge of any railway with standard track gauge.

The loading gauge differs around the world. The smallest loading gauge (for a railway of standard gauge track) is that of the London Underground's deep tube lines. The largest loading gauge is that of the Channel Tunnel between Great Britain and France. ImageMetadata File history File links Download high resolution version (1600x1200, 850 KB) A Metropolitan Line A stock sub-surface gague train passes a smaller Piccadilly Line 1973 tube stock train. ... ImageMetadata File history File links Download high resolution version (1600x1200, 850 KB) A Metropolitan Line A stock sub-surface gague train passes a smaller Piccadilly Line 1973 tube stock train. ... As railways developed and expanded one of the key issues to be decided was that of the rail gauge (the distance between the two rails of the track) which should be used. ... As railways developed and expanded one of the key issues to be decided was that of the rail gauge (the distance between the two rails of the track) which should be used. ... The London Underground is an underground railway system - also known as a rapid transit system - that serves a large part of Greater London, United Kingdom and some neighbouring areas. ... The British terminal at Cheriton in west Folkestone, from the Pilgrims Way. ...

The loading gauge on the main lines of Great Britain, where rail transport started, is quite small as early engineers could not predict the future requirements for larger trains and faced huge technical challenges building railways in this period. In mainland Europe, lines tend to conform to the slightly larger Berne gauge and loading gauges in the North America tend to be larger still. The Russian (including Finnish and ex-Soviet) and the Chinese loading gauges are also large, whereas the Scandinavian come in between.

Britain

British loading gauge is 9 ft (2743 mm) wide by 11 ft (3353 mm) high on the sides, rising to a 13 ft 6 in (4115 mm) centre. Below platform level (the lower 3 ft 6 in or 914 mm) the vehicle can be no wider than 8 ft 8 in (2642 mm). Some lines, particularly the Hastings Line, had even narrower loading gauges. By contrast the European (Berne) loading gauge is usually 10 ft 2 in (3150 mm) wide by 10 ft 5 in (3175 mm) rising to 14 ft 0½ in (4280 mm) in the centre. This is a clearance envelope on a curve of 250 m (820 ft 2.5 in) radius. The Hastings Line is a railway line in Kent and Sussex, which links Hastings with Tonbridge, and from there into London via Sevenoaks. ...

British loading gauges currently use a classification system prefixed with 'W'. This ranges, in height at least, from W6a to W12. W6a, formerly British Rail W6, is available over the majority of the British rail network.^[1] A strategy was adopted in 2004 to guide enhancements of loading gauges.^[2]

North America

Double-stack container cars require the highest loading gauge in common use in North America.

The American loading gauge for freight cars on the North American rail network is generally based on standards set by the Association of American Railroads (AAR). The most widespread standards are AAR Plate B and AAR Plate C, but higher loading gauges have been introduced on selected routes to accommodate rolling stock that make better economic use of the network, such as auto carriers and double-stack container cars. Image File history File linksMetadata Download high resolution version (1024x768, 280 KB)DTTX 724681, a portion of a Pacer Stacktrain (Concord, CA) 5-unit container car (a specialized type of gondola) seen passing through Rochelle Railroad Park, Rochelle, Illinois, on May 29, 2005. ... Image File history File linksMetadata Download high resolution version (1024x768, 280 KB)DTTX 724681, a portion of a Pacer Stacktrain (Concord, CA) 5-unit container car (a specialized type of gondola) seen passing through Rochelle Railroad Park, Rochelle, Illinois, on May 29, 2005. ... A railroad car (or, more briefly, car, not to be confused with railcar), also known as an item of rolling stock, is a vehicle on a railroad (or railway) that is not a locomotive — one that provides another purpose than purely haulage, although some types of car are powered. ... A World War II era print advertisement for the Association of American Railroads (AAR). ...

Freight

AAR Plate B allows cars 15 ft 1 in (4597 mm) high and 10 ft 8 in (3251 mm) wide with 41 ft 3 in (12.573 m) truck (bogie) centers. When the distance between trucks exceeds 41 ft 3 in, the width is decreased according to graph AAR Plate B-1. AAR Plate C allows cars 15 ft 6 in (4724 mm) high and 10 ft 8 in (3251 mm) wide with 46 ft 3 in (14.097 m) truck (bogie) centers. When the distance between trucks exceeds 46 ft 3 in, the width is decreased according to graph AAR Plate C-1. A bogie is a wheeled wagon or trolley. ...

Technically, 15 ft 1 in (Plate B) is still the maximum and the circulation of 15 ft 6 in (Plate C) is somewhat restricted, but the frequency of excess-height rolling stock, at first ~18 ft (5486 mm) piggybacks and hicube boxcars then later autoracks, airplane parts cars as well as 20 ft 2 in (6147 mm) high double-stacked containers in container well cars, means that many, but not all, lines are now designed for a higher loading gauge. The width of these extra height cars is covered by Plate C-1. However, additional height restrictions apply to the Long Island Rail Road (LIRR) which can not even handle the 15 ft 1 in height, to the Metro-North Railroad and to Amtrak's Northeast Corridor. For other uses, see Boxcar (disambiguation). ... An autorack, also known as an auto carrier, is a specialized piece of railroad rolling stock used to transport unladen automobiles. ... For other uses, see Boxcar (disambiguation). ... Containers on the Port of Singapore. ... A railroad gondola seen at Rochelle, Illinois. ... LIRR redirects here. ... The Metro-North Commuter Railroad Company, or MTA Metro-North Railroad, or, more commonly, Metro-North, is a suburban commuter rail service that is run and managed by an authority of New York State, the Metropolitan Transportation Authority, or, more simply, the MTA. Metro-North runs service between New York... The high-speed Acela Express in West Windsor, New Jersey. ... Most of the NEC (those sections shown in red, except Boston to the Rhode Island state line) is owned by Amtrak. ...

Passenger

The standard North American passenger railcar is 10 ft 6 in (3200 mm) wide by 14 ft 6 in (4420 mm) high and measures 85 ft 0 in (25.908 m) over coupler faces with 59 ft 6 in (18.136 m) bogie (truck) centers or 86 ft 0 in (26.213 m) over coupler faces with 60 ft 0 in (18.288 m) bogie (truck) centers. In the 1940s and 1950s, the American passenger car loading gauge was increased to a 16 ft 6 in (5029 mm) height in the West to accommodate dome cars and later Superliners and other double-decker trains. Amtrak's Northeast Corridor, especially Pennsylvania Station which Amtrak owns, but shares with the LIRR, can not handle the higher double-deckers, but can handle 14 ft 6 in (4420 mm) high "split level" cars. On the Metro-North Railroad and the Long Island Rail Road (including Pennsylvania Station) the 10" (254 mm) high, above top of rail, safety cover decreases the structure gauge and in turn the loading gauge from top of rail to 11" (280 mm) above top of rail as measured on a 20° curve, which means a radius of 297.94' (87.764 m). These dimensions apply only to North American commuter lines that are used by main line passenger trains and freight trains as well. See also "Additional infrastructure restrictions" in Disadvantages of third rail. Restored passenger cars on display at the Mid-Continent Railway Museum in North Freedom, WI. A passenger car is a piece of railroad rolling stock that is designed to carry passengers. ... Former California Zephyr dome car in excursion train service with the Inland Lakes Railway -- Plymouth, Florida. ... This converted Auto Train lounge shows the typical exterior of Superliner cars. ... Double-deck rail car operated by GO Transit, Ontario, Canada Bilevel car is a clever design to solve the problem of increasing passenger capacity on railcars, without squeezing more (smaller) seats into the same space and/or decreasing the pitch (distance between seats). ... A double decker is a bus, airplane, train, tram, ferry, or any public transit vehicle that has two levels for passengers, one deck above the other. ... Pennsylvania Station (commonly known as Penn Station) is the major intercity rail station and a major commuter rail hub in New York City. ... The Structure gauge, also called the minimum clearance outline, is the minimum size of tunnels and bridges as well as the minimum size of the doors that allow a rail siding access into a warehouse. ... Third rail at the West Falls Church Metro stop in Washington, D.C., electrified to 750 volts. ...

Not all railways were built to standard (generous) loading gauges. Many narrow gauge railways also have a very small loading gauge in order to keep construction costs low. The choice of loading gauge represented a significant engineering decision to trade construction and maintenance costs against train size (and thus capacity), and also led to some unusual solutions to problems, including the Fairlie locomotives. Fairlie locomotive built for Burma Railways by the Vulcan Foundry Co. ...

References

1. ^ Rail Safety and Standards Board, Guidance on Gauging, October 2004
2. ^ Strategic Rail Authority Gauging Policy, undated but probably 2005

See also

• Clearance car
• Railway platform

This primitive clearance car of the D&RGW consists of a simple wooden outline. ... A railway platform is a section of pathway, alongside rail tracks at a train station, metro station or tram stop, at which passengers may board or alight from trains or trams. ...

External links

• Berne and all that (1992 diagram of European loading gauges) at crowsnest.com (Internet Explorer cannot display the webpage, and the diagram may not show up anyway)
• AAR "plate" loading gauge diagrams compared to UIC (pdf & Autocad)
• Railway Loading Gauges at Joyce's World of Transport Eclectica
• Loading Gauges at The Self Site