Dynamic Envelope

A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and keep clear of platforms, trackside buildings and structures. Classification systems vary between different countries, and gauges may vary across a network, even if the track gauge is uniform.

The term loading gauge can also be applied to the maximum size of road vehicles in relation to tunnels, overpasses and bridges, and doors into automobile repair shops, bus garages, filling stations, residential garages, multi-storey car parks and warehouses.

A related but separate gauge is the structure gauge, which sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. The difference between these two gauges is called the clearance. The specified amount of clearance makes allowance for wobbling of rail vehicles at speed.

Overview

The loading gauge restricts the size of passenger coaches, goods wagons (freight cars) and shipping containers that can travel on a section of railway track. It varies across the world and often within a single railway system. Over time there has been a trend towards larger loading gauges and more standardization of gauges; some older lines have had their structure gauges enhanced by raising bridges, increasing the height and width of tunnels and making other necessary alterations. Containerisation and a trend towards larger shipping containers has led rail companies to increase structure gauges to compete effectively with road haulage.

The term "loading gauge" can also refer to a physical structure, sometimes using electronic detectors using light beams on an arm or gantry placed over the exit lines of goods yards or at the entry point to a restricted part of a network. The devices ensure that loads stacked on open or flat wagons stay within the height/shape limits of the line's bridges and tunnels, and prevent out-of-gauge rolling stock entering a stretch of line with a smaller loading gauge. Compliance with a loading gauge can be checked with a clearance car. In the past, these were simple wooden frames or physical feelers mounted on rolling stock. More recently, laser beams are used.

The loading gauge is the maximum size of rolling stock. It is distinct from the minimum structure gauge, which sets limits to the size of bridges and tunnels on the line, allowing for engineering tolerances and the motion of rail vehicles. The difference between the two is called the clearance. The terms "dynamic envelope" or "kinematic envelope" – which include factors such as suspension travel, overhang on curves (at both ends and middle) and lateral motion on the track – are sometimes used in place of loading gauge.

The height of platforms is also a consideration for the loading gauge of passenger trains. Where the two are not directly compatible, stairs may be required, which will increase loading times. Where long carriages are used at a curved platform, there will be gaps between the platform and the carriage door, causing risk. Problems increase where trains of several different loading gauges and train floor heights use (or even must pass without stopping at) the same platform.

The size of load that can be carried on a railway of a particular gauge is also influenced by the design of the rolling stock. Low-deck rolling stock can sometimes be used to carry taller shipping containers on lower gauge lines although their low-deck rolling stock cannot then carry as many containers.

Rapid Transit (metro) railways generally have a very small loading gauge, which reduces the cost of tunnel construction. These systems only use their own specialised rolling stock.

Out of gauge

Larger ''out-of-gauge'' loads can also sometimes be conveyed by taking one or more of the following measures:
* Operate at low speed, especially in places with limited clearance, such as platforms.
* Cross over from a track with inadequate clearance to another track with greater clearance, even if there is no signalling to allow this.
* Prevent operation of other trains on adjacent tracks.
* Use refuge loops to allow trains to operate on other tracks.
* Use of Schnabel cars (special rolling stock) that manipulate the load up and down or left and right to clear obstacles.
* Remove (and later replace) obstacles.
* Use gauntlet track to shift the train to side or center.
* For locomotives that are too heavy, ensure that fuel tanks are nearly empty.
* Turn off power in overhead wiring or in the third rail (use diesel locomotive)
* Permanently adapt a certain route to larger gauge if there is repeated need for such trains.

History

The loading gauge on the main lines of Great Britain, most of which were built before 1900, is generally smaller than in other countries. In mainland Europe, the slightly larger Berne gauge (Gabarit passe-partout international, PPI) was agreed to in 1913 and came into force in 1914. As a result, British trains have noticeably and considerably smaller loading gauges and, for passenger trains, smaller interiors, despite the track being standard gauge, which is in line with much of the world.

This often results in increased costs for purchasing new trainsets or locomotives as they must be specifically designed for the existing British network, rather than being purchased "off-the-shelf". For example, the new trains for HS2 have a 50% premium applied to the "classic compatible" sets that will be "compatible" with the current (or "classic") rail network loading gauge as well as the HS2 line. The "classic compatible" trainsets will cost £40million per trainset whereas the HS2-only stock (built to European loading gauge and only suitable to operate on HS2 lines) will cost £27M per trainset despite the HS2-only stock being physically larger.

It was recognized even during the nineteenth century that this would pose problems and countries whose railroads had been built or upgraded to a more generous loading gauge pressed for neighboring countries to upgrade their own standards. This was particularly true in continental Europe where the Nordic countries and Germany with their relatively generous loading gauge wanted their cars and locomotives to be able to run throughout the standard gauge network without being limited to a small size. France, which at the time had the most restrictive loading gauge ultimately compromised giving rise to Berne gauge which came into effect just before World War I.

Military railways were often built to particularly high standards, especially after the American Civil War and the Franco-Prussian War showed the importance of railroads in troop transport as well as mobilization. The Kaiserreich was particularly active in the construction of military railways which were often built with great expense to be as flat, straight and permissive in loading gauge as possible while bypassing major urban areas, making those lines of little use to civilian traffic, particularly civilian passenger traffic. However, all those aforementioned factors have in some cases led to the subsequent abandoning of those railroads.

Standard loading gauges for standard track gauge lines

International Union of Railways (UIC) Gauge

The International Union of Railways (UIC) has developed a standard series of loading gauges named A, B, B+ and C.
* PPI – the predecessor of the UIC gauges had the maximum dimensions with an almost round roof top.
* UIC A: The smallest (slightly larger than PPI gauge). Images do not load Maximum dimensions .
* UIC B: Most of the high-speed TGV tracks in France are built to UIC B. Maximum dimensions .
* UIC B+: New structures in France are being built to UIC B+. Up to has a shape to accommodate tractor-trailers loaded with ISO containers.
* UIC C: The Central European gauge. In Germany and other central European countries, the railway systems are built to UIC C gauges, sometimes with an increment in the width, allowing Scandinavian trains to reach German stations directly, originally built for Soviet freight cars. Maximum dimensions .

Europe

European standards

In the European Union, the UIC directives were supplanted by ERA Technical Specifications for Interoperability (TSI) of European Union in 2002, which has defined a number of recommendations to harmonize the train systems. The TSI Rolling Stock (2002/735/EC) has taken over the UIC Gauges definitions defining Kinematic Gauges with a reference profile such that Gauges GA and GB have a height of (they differ in shape) with Gauge GC rising to allowing for a width of of the flat roof. All cars must fall within an envelope of wide on a radius curve. The TGVs, which are wide, fall within this limit.

The designation of a GB+ loading gauge refers to the plan to create a pan-European freight network for ISO containers and trailers with loaded ISO containers. These container trains ('' piggy-back trains'') fit into the B envelope with a flat top so that only minor changes are required for the widespread structures built to loading gauge B on continental Europe. Currently, some structures on the British Isles are extended to fit with GB+ as well, where the first lines to be rebuilt start at the Channel Tunnel.

Owing to their historical legacies, many member states' railways do not conform to the TSI specification. For example, Britain's role at the forefront of railway development in the 19th century has condemned it to the small infrastructure dimensions of that era. Conversely, the s of countries that were satellites of the former Soviet Union, such as those in Finland, are much larger than the TSI specification. Other than for GB+, they are not likely to be retrofitted, given the enormous cost and disruption that would be entailed.

Double-decker carriages

A specific example of the value of these loading gauges is that they permit double decker passenger carriages. Although mainly used for suburban commuter lines, France is notable for using them on its high speed TGV services: the SNCF TGV Duplex carriages are high, and the Netherlands and Switzerland feature large numbers of double decker intercity trains as well.

Great Britain

Great Britain has (in general) the most restrictive loading gauge (relative to track gauge) in the world. That is a legacy of the British railway network being the world's oldest, and of having been built by a plethora of different private companies, each with different standards for the width and height of trains. After nationalisation, a standard static gauge W5 was defined in 1951 that would virtually fit everywhere in the network. The W6 gauge is a refinement of W5, and the W6a changed the lower body to accommodate third-rail electrification. While the upper body is rounded for W6a with a static curve, there is an additional small rectangular notch for W7 to accommodate the transport of ISO containers, and the W8 loading gauge has an even larger notch spanning outside of the curve to accommodate the transport of ISO containers. While W5 to W9 are based on a rounded roof structure, those for W10 to W12 define a flat line at the top and, instead of a strict static gauge for the wagons, their sizes are derived from dynamic gauge computations for rectangular freight containers.

Network Rail uses a ''W'' loading gauge classification system of freight transport ranging from W6A (smallest) through W7, W8, W9, W9Plus, W10, W11 to W12 (largest). The definitions assume a common "lower sector structure gauge" with a common freight platform at above rail.

In addition, gauge C1 provides a specification for standard coach stock, gauge C3 for longer Mark 3 coaching stock, gauge C4 for Pendolino stock and gauge UK1 for high-speed rail. There is also a gauge for locomotives. The size of container that can be conveyed depends both upon the size of the load that can be conveyed and the design of the rolling stock.

* W6a: Available over the majority of the British rail network.
* W8: Allows standard high shipping containers to be carried on standard wagons.
* W9: Allows high ''Hi-Cube'' shipping containers to be carried on " Megafret" wagons that have lower deck height with reduced capacity. At wide, it allows for wide ''Euro'' shipping containers, which are designed to carry Euro-pallets efficiently
* W10: Allows high ''Hi-Cube'' shipping containers to be carried on standard wagons and also allows wide ''Euro'' shipping containers. Larger than UIC A.
* W11: Little used but larger than UIC B.
* W12: Slightly wider than W10 at to accommodate refrigerated containers. Recommended clearance for new structures, such as bridges and tunnels.
* UIC GC: Channel Tunnel and Channel Tunnel Rail Link to London; with proposals to enable GB+ northwards from London via an upgraded Midland Main Line.

A strategy was adopted in 2004 to guide enhancements of loading gauges and in 2007 the freight route utilisation strategy was published. That identified a number of key routes where the loading gauge should be cleared to W10 standard and, where structures are being renewed, that W12 is the preferred standard.

Height and width of containers that can be carried on GB gauges (height by width). Units as per source material.
* W9: by
* W10: by
* W11: by
* W12: by

=Tube lines

=
* City and South London Railway was built with tunnels of only diameter. Enlarged for Northern line to
* Central line with tunnels of , increased on curves, reduced to near to stations. This makes Central line trains unique on the London Underground system because, although the loading gauge of the rolling stock is the same as the other 'tube' lines, the smaller size of the tunnel requires that the positive conductor rail is higher than on all other lines.

A Parliamentary committee headed by James Stansfeld then reported on 23 May 1892, "The evidence submitted to the Committee on the question of the diameter of the underground tubes containing the railways has been distinctly in favour of a minimum diameter of ". After that, all tube lines were at least that size.

* Piccadilly line with tunnels of
* Victoria line with tunnels of ; enlarged to reduce air friction.
* Glasgow Subway with tunnels of and a unique track gauge of only .
* Tyne and Wear Metro with tunnels of ; built to mainline rail network standards.

Sweden

Sweden uses shapes similar to the Central European loading gauge but trains allowed to be much wider.

There are three main classes in use (width × height):
* Class SE-A is . Similar to OPS-NL (Netherlands), Victorian (Australia) and Chinese loading gauges.
* Class SE-B is . Similar to Norwegian loading gauge.
* Class SE-C is with a completely flat roof top. Similar to OPS-GC (Netherlands) loading gauge.

Malmbanan north of Kiruna was the first electrified railway line in Sweden and has limited height clearance (SE-B) because of snow shelters. On the rest of the network belonging to Trafikverket, the structure gauge accepts cars built to SE-A and thus accepts both cars built to UIC GA and GB. Some modern electric multiple-units, like Regina X50 with derivatives, are somewhat wider than normally permitted by SE-A at . This is generally acceptable as the extra width is above normal platform height, but it means that they can not use the high platforms that Arlanda Express uses ( Arlanda Central Station has normal clearances). The greater width allows sleeping cars in which tall people can sleep with straight legs and feet, which is not the case on the continent.

Netherlands

In the Netherlands, a similar shape to the UIC C is used that rises to in height. The trains are wider allowing for width similar to Sweden. About one third of the Dutch passenger trains use bilevel rail cars. However, Dutch platforms are much higher than Swedish ones.

= Betuweroute

=
* Betuweroute: to allow double stacked container trains in the future. The present overhead line does not allow this height, as it has to follow standards.

Channel Tunnel

* Channel Tunnel:

North America

Freight

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) Mechanical Division. The most widespread standards are ''AAR Plate-B'' and ''AAR Plate-C'', but higher loading gauges have been introduced on major routes outside urban centers to accommodate rolling stock that makes better economic use of the network, such as auto carriers, hi-cube boxcars, and double-stack container loads. The maximum width of on and truck centers is valid on a radius curve.

Listed here are the maximum heights and widths for cars. However, the specification in each plate shows a car cross section that is chamfered at the top and bottom, meaning that a compliant car is not permitted to fill an entire rectangle of the maximum height and width.

Technically, Plate B is still the maximum height and truck center combination and the circulation of Plate C is somewhat restricted. The prevalence of excess-height rolling stock, at first ~ piggybacks and hicube boxcars, then later autoracks, airplane-parts cars, and flatcars for hauling Boeing 737 fuselages, as well as high double-stacked containers in container well cars, has been increasing. This means that most, if not all, lines are now designed for a higher loading gauge. The width of these extra-height cars is covered by Plates C-1, D-1 and D-2.

All the Class I rail companies have invested in longterm projects to increase clearances to allow double stack freight. The mainline North American rail networks of the Union Pacific, the BNSF, the Canadian National, and the Canadian Pacific, have already been upgraded to AAR Plate K. This represents over 60% of the Class I rail network.

Passenger service

The old standard North American passenger railcar is wide by high and measures over coupler pulling faces with truck centers, or over coupler pulling faces with truck centers. In the 1940s and 1950s, the American passenger car loading gauge was increased to a height throughout most of the country outside the Northeast, to accommodate dome cars and later Superliners and other bilevel commuter trains. Bilevel and Hi-level passenger cars have been in use since the 1950s, and new passenger equipment with a height of has been built for use in Alaska and the Canadian Rockies. The structure gauge of the Mount Royal Tunnel limits the height of bilevel cars to .

New York City Subway

The New York City Subway is an amalgamation of three former constituent companies, and while all are standard gauge, inconsistencies in loading gauge prevent cars from the former BMT and IND systems ( B Division) from running on the lines of the former IRT system ( A Division), and vice versa. This is mainly because IRT tunnels and stations are approximately narrower than the others, meaning that IRT cars running on the BMT or IND lines would have platform gaps of over between the train and some platforms, whereas BMT and IND cars would not even fit into an IRT station without hitting the platform edge. Taking this into account, all maintenance vehicles are built to IRT loading gauge so that they can be operated over the entire network, and employees are responsible for minding the gap.

Another inconsistency is the maximum permissible railcar length. Cars in the former IRT system are . Railcars in the former BMT and IND can be longer: on the former Eastern Division, the cars are limited to , while on the rest of the BMT and IND lines plus the Staten Island Railway (which uses modified IND stock) the cars may be as long as .

Boston (MBTA)

The MBTA's rapid transit system is composed of four unique subway lines; while all lines are standard gauge, inconsistencies in loading gauge, electrification, and platform height prevent trains on one line from being used on another. The first segment of the Green Line (known as the Tremont Street Subway) was constructed in 1897 to take the streetcars off Boston's busy downtown streets. When the Blue Line opened in 1904, it only ran streetcar services; the line was converted to rapid transit in 1924 due to high passenger loads, but the tight clearances in the tunnel under the Boston Harbor required narrower and shorter rapid transit cars. The Orange Line was originally built in 1901 to accommodate heavy rail transit cars of higher capacity than streetcars. The Red Line was opened in 1912, designed to handle what were for a time the largest underground transit cars in the world.

Los Angeles (LACMTA)

The Los Angeles Metro Rail system is an amalgamation of two former constituent companies, the Los Angeles County Transportation Commission and the Southern California Rapid Transit District; both of those companies were responsible for planning the initial system. It is composed of two heavy rail subway lines and several light rail lines with subway sections; while all lines are standard gauge, inconsistencies in electrification and loading gauge prohibit the light rail trains from operating on the heavy rail lines, and vice versa. The LACTC-planned Blue Line was opened in 1990 and partially operates on the route of the Pacific Electric interurban railroad line between downtown Los Angeles and Long Beach, which used overhead electrification and street-running streetcar vehicles. The SCRTD-planned Red Line (later split into the Red and Purple lines) was opened in 1993 and was designed to handle high-capacity heavy rail transit cars that would operate underground. Shortly after the Red Line began operations, the LACTC and the SCRTD merged to form the LACMTA, which became responsible for planning and construction of the Green, Gold, Expo, and K lines, as well as the Purple Line Extension and the Regional Connector.

Asia

Major trunk raillines in East Asian countries, including China, North Korea, South Korea, as well as the Shinkansen of Japan, have all adopted a loading gauge of maximum width and can accept the maximum height of .

China

The max. height, width, and length of general Chinese rolling stock are , and , with an extra ''out-of-gauge'' load allowance of height and width with some special shape limitation, corresponding to a structure gauge of . China is building numerous new railways in sub-Saharan Africa and Southeast Asia (such as in Kenya and Laos), and these are being built to "Chinese Standards". This presumably means track gauge, loading gauge, structure gauge, couplings, brakes, electrification, etc. An exception may be double stacking, which has a height limit of . Metre gauge in China has a gauge of .

Japan, standard gauge

Translation of legend:

Trains on the Shinkansen network operate on track and have a loading gauge of maximum width and maximum height. However some Shinkansen trains are higher, such as E1 Series Shinkansen. This allows the operation of double-deck high-speed trains.

''Mini Shinkansen'' (former conventional narrow gauge lines that have been regauged into ) and some private railways in Japan (including some lines of the Tokyo subway and all of the Osaka Metro) also use standard gauge; however, their loading gauges are different.

The rest of Japan's system is discussed under narrow gauge, below.

Hong Kong

South Korea

The body frame may have a maximum height of and a maximum width of with additional installations allowed up to . That width of 3,400 mm is only allowed above as the common passenger platforms are built to former standard trains of in width.

Philippines

There is currently no uniform standard for loading gauges in the country and both loading gauges and platform heights vary by rail line.

The North–South Commuter Railway allows passenger trains with a carbody width of and a height of . Additional installations shall also be allowed up to at a platform height of where it is limited by half-height platform screen doors. Above the platform gate height of above the platforms, out-of-gauge installations can be further maximized to the Asian standard at .NSCR and SLH bid documents at

Meanwhile, the PNR South Long Haul will follow the Chinese gauge and therefore use a larger carbody width of from the specifications of passenger rolling stock, and a height of per P70-type boxcar specifications.

Africa

Some of the new railways being built in Africa allow for double-stacked containers, the height of which is about depending on the height of each container or plus the height of the deck of the flat wagon about totalling . This exceeds the China height standard for single stacked containers of . Additional height of about is needed for overhead wires for 25 kV AC electrification.

The permissible width of the new African standard gauge railways is .

Australia

The standard gauge lines of New South Wales Government Railways (NSWGR) allowed for a width of until 1910, after a conference of the states created a new standard of , with corresponding increase in track centres. The narrow widths have mostly been eliminated, except, for example, at the mainline platforms at Gosford railway station and some sidings. The longest carriages are .

The Commonwealth Railways adopted the national standard of when they were established in 1912, although no connection with New South Wales was made until 1970.

A double deck Electric Tangara train of the late 1980s was wide. Track centres from Penrith railway station to Mount Victoria railway station and Gosford and Wyong have been gradually widened to suit. The proposed Korean manufactured intercity sets are however wide, so further, costly modification was required beyond Springwood, which was completed in 2020.

The 1968 built Kwinana- Kalgoorlie standard gauge railway in Western Australia was built with a loading gauge of 12 ft (3.66 m) wide and 20 ft (6.1 m) tall to allow for trailer on flatcar (TOFC) traffic.

Broad gauge

Indian Gauge

* The smallest loading gauge for a railway of the gauge track is Delhi Metro, which is wide and high.
* Indian Railways has a maximum passenger loading gauge of 3,660 mm and has a freight loading gauge of 3,250 mm with development allowing a loading gauge of 3,710 mm.
* Sri Lankan Railways has a loading gauge of between 3200 mm and 4267 mm.

Russian Gauge

In Finland, the rail cars can be up to wide with a permitted height from on the sides to in the middle. The track gauge is , differing from the Russian track gauge.

The Russian loading gauges are defined in standard GOST 9238 (ГОСТ 9238–83, ГОСТ 9238–2013) with the current 2013 standard named "Габариты железнодорожного подвижного состава и приближения строений" (construction of rolling stock clearance diagrams fficial English title. It was accepted by the Interstate Council for Standardization, Metrology and Certification to be valid in Russia, Belarus, Moldova, Ukraine, Uzbekistan and Armenia.

The standard defines static envelopes for trains on the national network as T, T_c and T_pr. The static profile 1-T is the common standard on the complete 1520 mm rail network including the CIS and Baltic states. The structure clearance is given as S, S_p and S₂₅₀. There is a tradition that structure clearance is much bigger than the common train sizes. For international traffic, the standard references the kinematic envelope for GC and defines a modified GC_ru for its high-speed trains. For other international traffic, there are 1-T, 1-VM, 0-VM, 02-VM and 03-VM_st/03-VM_k for the trains and 1-SM for the structure clearance.

The main static profile T allows for a maximum width of rising to a maximum height of . The profile T_c allows that width only at a height of , requiring a maximum of below , which matches with the standard for train platforms (with a height of ). The profile T_pr has the same lower frame requirement but reduces the maximum upper body width to . The more universal profile 1-T has the complete body at a maximum width of still rising to a height of . Exceptions shall be double-stacking, maximum height shall be or .

The structure gauge S requires buildings to be placed at minimum of from the track centreline. Bridges and tunnels must have a clearance of at least wide and high. The structure gauge S_p for passenger platforms allows only above (the common platform height) requiring a width of below that line. The exceptions shall be double-stacking, minimum overhead wiring height must be (for maximum vehicle height of ) or (for maximum vehicle height of ).

The main platform is defined to have a height of at a distance of from the center of the track to allow for trains with profile T. Low platforms at a height of may be placed at from the center of the track. A medium platform is a variant of the high platform but at a height of . The latter matches with the TSI height in Central Europe. In the earlier standard from 1983, the profile T would only be allowed to pass low platforms at while the standard high platform for cargo and passenger platforms would be placed no less than from the center of the track. That matches with the T_c, T_pr and the universal 1-T loading gauge.

Iberian gauge

Irish Gauge

Ireland and Nortern Ireland

Australia

Brazil

Narrow gauge

Narrow gauge railways generally have a smaller loading gauge than standard gauge ones, and this is a major reason for cost savings rather than the railgauge itself. For example, the Lyn locomotive of the Lynton and Barnstaple Railway is wide. By comparison, several standard gauge 73 class locomotives of the NSWR, which are wide, have been converted for use on cane tramways, where there are no narrow bridges, tunnels or track centres to cause trouble. The 6E1 locomotive of the South African Railways are wide.

A large numbers of railways using the gauge used the same rolling stock plans, which were wide.

Great Britain

Ffestiniog Railway

* gauge =
* width (brakevan mirrors) =
* width (brakevan body) =
* height =
* length = (carriage)

Lynton and Barnstaple Railway

* gauge =
* Lyn (locomotive) over headstocks
** length =
** width =
** height =
* Passenger
** length =
** width = wide,
** width over steps =
** height =

Japan, narrow gauge

Translation of legend:

The Japanese national network operated by Japan Railways Group employs narrow gauge . The maximum allowed width of the rolling stock is and maximum height is ; however, a number JR lines were constructed as private railways prior to nationalisation in the early 20th century, and feature loading gauges smaller than the standard. These include the Chūō Main Line west of Takao, the Minobu Line, and the Yosan Main Line west of Kan'onji ( height). Nevertheless, advances in pantograph technology have largely eliminated the need for separate rolling stock in these areas.

There are many private railway companies in Japan and the loading gauge is different for each company.

South Africa

The South African national network employs gauge. The maximum width of the rolling stock is and maximum height is , which is greater than the normal British loading gauge for standard gauge vehicles.

New Zealand

The railways use gauge. The maximum width of the rolling stock is and maximum height is .

Other

* gauge for the United Kingdom, Sierra Leone
* minimum radius
* width (see Everard Calthrop)
* wagon length freight over headstocks
* wagon length passenger over headstocks
* tank engine length over headstocks

Structure gauge

The structure gauge, which refers to the dimensions of the lowest and narrowest bridges or tunnels of the track, complements the loading gauge, which specifies the tallest and widest allowable vehicle dimensions. There is a gap between the structure gauge and loading gauge, and some allowance needs to be made for the dynamic movement of vehicles (sway) to avoid mechanical interference causing equipment and structural damage.

Out of gauge

While it may be true that trains of a particular loading gauge can travel freely over tracks of a matching structure gauge, in practice, problems can still occur. In an accident at Moston station, an old platform not normally used by freight trains was hit by a train that wasn't within its intended W6a gauge because two container fastenings were hanging over the side. Analysis showed that the properly configured train would have passed safely even though the platform couldn't handle the maximum design sway of W6a. Accepting reduced margins for old construction is normal practice if there have been no incidents but if the platform had met modern standards with greater safety margin the out of gauge train would have passed without incident.

Trains larger than the loading gauge, but not too large, can operate if the structure gauge is carefully measured, and the trip is subject to various special regulations.

Gallery

Image:Lichtraumprofilbrücke (001).JPG, Calibration bridge, used to indicate the maximum height of vehicles on a highway.
File:BS Ladelehre Westbahnhof.JPG, German equipment outline gauge
File:Lademass.jpg, Template to check if the load is exactly within the loading gauge
File:Pont Ducharme Est.jpg, Structure gauge limiting the height of vehicles for Ducharme Bridge.
File:Loading gauge at Moccone.jpg, Equipment outline gauge at Moccone
File:Loading Gauge Eritrea.jpg, Eritrean loading gauge

See also

* Berne gauge
* Bridge
* Clearance car
* Clearance space
* Cut
* Platform gap
* Over weight
* Railway platform height
* Ride height
* Structure gauge
* Tunnel

References

Further reading

* '' Jane's World Railways'' yearbook contains many though not all loading gauge diagrams.

External links

2002/732/EC: Commission Decision of 30 May 2002 concerning the technical specification for interoperability relating to the infrastructure subsystem of the trans-European high-speed rail system




Railway industrial Clearance Association




Railway line clearances and car dimensions including weight limitations of railroads in the United States, Canada, Mexico and Cuba.

AAR plates with UIC


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Rail loading gauge