Loading gauge


A []loading gauge defines the maximum height and width for railway vehicles and their loads to ensure that they can pass safely through tunnels, under bridges and keep clear of trackside buildings and structures. Classification systems vary between different countries and gauges may vary across a network, even if the track gauge remains constant.

Overview

The loading gauge restricts the size of passenger coaches, goods wagons 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. This is distinct from the structure gauge, which is the minimum size of bridges and tunnels, and must be larger to allow for engineering tolerances and car motion. 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 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 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.

Out of gauge

Larger out-of-gauge loads can also sometimes be conveyed by taking one or more of the following measures:
Rapid Transit railways generally have a very small loading gauge, which reduces the cost of tunnel construction. These systems only use their own specialised rolling stock.

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 was agreed to in 1913 and came into force in 1914. As a result, British trains have noticeably and considerably smaller loading gauges and smaller interiors, despite the track being standard gauge along with much of the world.
This results in increased costs for purchasing trains as they must be specifically designed for the 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 able to run on the rest of the network, meaning they will cost £40 million each rather than £27 million for the captive stock, despite the captive stock being larger.

Standard loading gauges for standard track gauge lines

International Union of Railways (UIC) Gauge

The International Union of Railways has developed a standard series of loading gauges named A, B, B+ and C.

European standards

In the European Union, the UIC directives were supplanted by ERA Technical Specifications for Interoperability of European Union in 2002, which has defined a number of recommendations to harmonize the train systems. The TSI Rolling Stock has taken over the UIC Gauges definitions defining Kinematic Gauges with a reference profile such that Gauges GA and GB have a height of 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 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.
Many member states' legacy railways, notably those in Great Britain, do not conform to the TSI specification and, given the cost and disruption entailed, are not likely to be retrofitted other than for GB+.

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 the most restrictive loading gauge in the world. This is a legacy of the British railway network being the world's oldest, and 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 to 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 through W7, W8, W9, W9Plus, W10, W11 to W12. 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 MkIII 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.
A strategy was adopted in 2004 to guide enhancements of loading gauges and in 2007 the freight route utilisation strategy was published; this 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. Units as per source material.
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 11 ft. 6 in." After that, all tube lines were at least that size.
Sweden uses shapes similar to the Central European loading gauge but trains are wider. There are three main classes in use :
Malmbanan north of Kiruna was the first electrified railway line in Sweden and has limited height clearance 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. 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.
When building new railways or extensive reinvestments are made to the existing railway infrastructure, the gauge is expanded to SE-C that also accepts UIC GC. The structure gauge on the bulk of the system already allows large cars built to SE-C, albeit with restrictions and a special permit. The remaining limitation is the track circuits, the blocks are not dimensioned for the extra width and a large car placed to close to a turnout at a passing loop may intrude on the structure envelope of the through line. As a stop-gap this is generally solved by adding an extra normal-sized car at the tail-end to ensure that no part of the consist obstruct the space needed by passing trains. The larger cars are also barred from using certain industrial spurs leading to warehouses or loading docks built for the narrower cars. The SE-C loading gauge is the future European standard, for the Rail Baltica II and the Narvik to Tel-Aviv train routes including the fixed rail links between Sweden and Poland and the second Marmaray fixed rail link.

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 double-decker railcars. However, Dutch platforms are much higher than Swedish ones.

Betuweroute and Channel Tunnel

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 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.
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 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 Plate C-1.
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 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 double-decker 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. See Bilevel rail car. 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 from running on the lines of the former IRT system, 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 as of 2013, but can be as long as. 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 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 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. Nowadays, 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 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 Crenshaw 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 Chinese rolling stock are, and. China is building numerous new railways in sub-Saharan Africa and Southeast Asia, 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.

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.

Japan

Blue 1900-1919 Loading gauge gauge
Gray 1987 Loading gauge gauge
Green 1964 Shinkansen loading gauge gauge
Trains on the Shinkansen network operate on standard-gauge track and have a loading gauge of maximum width and maximum height. However some Shinkansen trains are wider, such as E1 Series Shinkansen. This allows the operation of double-deck high-speed trains.
Mini Shinkansen and some private railways in Japan 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 South Korean national network has the same loading gauge as Japanese Shinkansen. 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.

Australia

The standard gauge lines of New South Wales Government Railways 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.
The height of the NSW loading gauge just happens to allow for double decker trains in Sydney, while the Victorian loading gauge, which is similar to Swedish SE-A loading gauge, is not quite tall enough to allow for double deck trains in Melbourne.
An NSW HV Composite Bogie Brake Van of 1884 was wide and tall.
A NSW single deck suburban electric train of the 1920s was wide, with track centres widened to to suit. With metrication in 1973, track centres of new work were widened to
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 will be required beyond Springwood.
The 1968 built Kwinana-Kalgoorlie standard gauge railway in Western Australia was built with a loading gauge of 12 ft wide and 20 ft tall to allow for trailer on flatcar traffic. Clearances across the Trans-Australian Railway were modified in the 1990s to a minimum standard of 21 ft 4 in to allow for double stacked containers. New ARTC standard for clearances above the railway is 23 ft 3.5 in.

Broad gauge

Indian Gauge

In Finland, the rails cars can be up to wide with a permitted height from on the sides to in the middle.
The Russian loading gauges are defined in standard GOST 9238 with the current 2013 standard named "Габариты железнодорожного подвижного состава и приближения строений". It was accepted by the to be valid in Russia, Belarus, Moldova, Ukraine, Uzbekistan and Armenia.
The standard defines static envelopes for trains on the national network as T, Tc and Tpr. 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, Sp 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 GCru for its high-speed trains. For other international traffic, there are 1-T, 1-VM, 0-VM, 02-VM and 03-VMst/03-VMk 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 Tc allows that width only at a height of, requiring a maximum of below, which matches with the standard for train platforms. The profile Tpr 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.
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 Sp for passenger platforms allows 4900 mm only above 1100 mm requiring a width of below that line.
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 200 mm 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 Tc, Tpr and the universal 1-T loading gauge.

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

Festiniog Railway

Japanese national network operated by Japan Railways Group employs narrow gauge and has maximum width of and maximum height of ; 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. 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, and has maximum width of and maximum height of, which is greater than the normal British loading gauge for standard gauge vehicles.

New Zealand

uses gauge. The maximum width is and maximum height is.

Other

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 to avoid mechanical interference causing equipment and structural damage.
The Structure gauge is always larger than the Loading gauge.

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.