Loading gauge

The clearance between train and tunnel is often small. London Underground train at Hendon.

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A loading gauge defines the maximum height and width for railway vehicles and their loads to ensure safe passage through bridges, tunnels and other structures.^[1] Classifications systems vary between different countries and gauges may vary across a network, even if the track gauge remains constant.

Introduction

London Underground operates differing loading gauges. Here a Metropolitan line A Stock sub-surface train (left) passes a Piccadilly line 1973 Stock tube train (right)

The loading gauge determines the sizes of passenger trains and the size of shipping container that can be conveyed on a section railway line and 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 with older lines having their gauges enhanced by raising bridges, increasing the height of tunnels and making other necessary alterations.Containerisation and a trend towards larger shipping containers has led rail companies to increase gauges to compete effectively with road haulage.

The term loading gauge can also refer to the physical structure, sometimes using an 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 restrict part of a network. The devices ensure that loads stacked on open or flat wagons stayed within the height/shape limits of the line's bridges and tunnels and prevent out-of-gauge rolling stock entering a region with a smaller loading gauge. Compliance with a loading gauge can be checked with a clearance car which in the past were simple wooden frames or physical feelers mounted on rolling stock and more recently lasers are used.

The loading gauge is maximum size of rolling stock which is distinct from the structure gauge which is minimum size of bridges and tunnels which 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 (at both ends and middle); and lateral motion on the track, are sometimes used in place of loading gauge.^{[citation needed]}

The height of platforms is also a consideration when considering the loading gauge of passenger trains. Where the two are not directly compatible then steps may be required which will increase loading times. Where long carriages are used on a curving platform gaps will occur between the platform and the carriage door causing additional 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 9 ft 6 in (2.90 m) shipping containers on lower gauge lines although there low-deck rolling-stock cannot then carry as many containers.

Larger out-of-gauge loads can also sometimes be conveyed by taking one or more of the following measures:

• operate at low speed, especially at places with limited clearance such as platforms
• crossover from 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 special rolling stock that manipulate the load up and down or left and right to clear obstacles.
• remove (and later replace) obstacles.
• for locomotives that are too heavy, ensure that fuel tanks are nearly empty.

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 in 1912 and came into force in 1914).^{[citation needed]} As a result, British (passenger) trains have smaller interiors, despite being standard gauge along with much of the world.

Standard gauges

International Union of Railways (IUC) Gauge

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

• UIC A: The smallest (slightly larger than PPI gauge).^[2] Maximum dimensions 3.15 m by 4.32 m.^[3]
• UIC B: Most of the high-speed TGV tracks in France are built to IUC B.^[2] Maximum dimensions 3.15 m by 4.32 m.^[4]
• UIC B+: New structures in France are being built to IUC B+.^[2]
• UIC C: The Central European gauge. In Germany and other central European countries the railway systems are built to IUC C gauges, sometimes with an increment in the width to allow for Scandinavian trains to reach German stations directly.^[2] Maximum dimensions 3.15 m by 4.65 m.^[5]
• UIC GB+: Is being used for some new European routes, including the Channel tunnel.^[6]

Europe

In Europe, the IUC directives were supplanted by ERA Technical Specifications for Interoperability 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 IUC Gauges definitions defining Kinematic Gauges with a references profile such that the Gauge GA and Gauge GB has a height of 4.35 m (they differ in shape) and Gauge GC to rise to 4.70 m allowing for a width of 3.08 m of the flat roof.^[7] All cars have a maximum outside width of 3.29 m (10.8 ft).

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, whereas the first lines to be rebuilt start at the channel tunnel.^[8]

• GA^[9]
• GB^[9]
• GB1^[9]
• GB2^[9]
• GB+^[8]
• GC^[9]
• GI3^[9]

Great Britain

Network Rail uses a W loading gauge classification system ranging from W6A (the smallest) through W7, W8, W9, W9Plus, W10, W11 to W12 (largest). In addition, C1 provides a specification for coach stock and 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.^[10]

• W6a: Available over the majority of the British rail network.^[11]
• W8: Allows standard 2.6 m (8.5 ft) high shipping containers to be carried on standard wagons.^[12]
• W9: Allows 2.9 m (9.5 ft) high Hi-Cube shipping containers to be carried on "Megafret" wagons which have lower deck height with reduced capacity.^[12] At 2.6 m wide it allows for 2.5 m wide Euro shipping containers^[13] which are designed to carry Euro-pallets efficiently^[14]
• W10: Allows 2.9 m (9.5 ft) high Hi-Cube shipping containers to be carried on standard wagons^[12] and also allows 2.5 m wide Euro shipping containers.^[13] Larger than UIC A.^[15]
• W11: Little used but larger than UIC B.^[15]
• W12: Slightly wider that W10 at 2.6 m to accommodate refrigerated containers.^[16] Recommended clearance for new structures, such as bridges and tunnels.^[17]
• UIC GB+: Has been implemented for the HS1 and the Channel Tunnel with a proposed extension on the Midland Main Line.^[6]

A strategy was adopted in 2004 to guide enhancements of loading gauges^[18] and in 2007 the Network Rail Freight Route Utilisation Strategy was published which identified a number of key routes where the loading gauge should be cleared to W10 standard and that where structures are being renewed that W12 is the preferred standard.^[17]

Height and width of containers that can be carried on GB gauges (Height/width). Units as per source material.

• W9: 9 ft (2.7 m) by 2.6 m
• W10: 9 ft 6 in (2.90 m) by 2.5 m
• W11: 9 ft 6 in (2.90 m) by 2.55 m
• W12: 9 ft 6 in (2.90 m) by 2.6 m^[13]

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) (Mechanical Division) ^[19]. 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.

Listed here are the maximum heights and widths for cars. However, the specification in each plate shows a car cross-section that tapers at the top and bottom, meaning that a compliant car is not permitted to fill an entire rectangle of the maximum height and width^[20].

• Plate B - 15 ft 1 in (4.6 m) high and 10 ft 8 in (3.3 m) wide with 41 ft 3 in (12.6 m) truck (bogie) centers. When the distance between trucks exceeds 41 ft 3 in (12.57 m), the width is decreased according to graph AAR Plate B-1.
• Plate C - 15 ft 6 in (4.7 m) high and 10 ft 8 in (3.25 m) wide with 46 ft 3 in (14.1 m) truck (bogie) centers. When the distance between trucks exceeds 46 ft 3 in (14.10 m), the width is decreased according to graph AAR Plate C-1.^[19]
• Plate D - 15 ft 1 in (4.6 m) high and 10 ft 8 in (3.3 m) wide, as with Plate B, but the car cross-section is larger at the top and a little larger at the bottom.
• Plate E - 15 ft 9 in (4.8 m) high and 10 ft 8 in (3.3 m) wide.
• Plate F - 17 ft 0 in (5.2 m) high and 10 ft 8 in (3.3 m) wide.
• Plate H - 20 ft 2 in (6.1 m) (Double Stacks).^[21]
• Plate J - ? (e.g., 89 ft 0 in (27.13 m) Long flatcars ^[22]).
• Plate K - 20 ft 2 in (6.1 m) high and 10 ft 8 in (3.3 m) wide (e.g., Autorack road vehicles on trains^[23]).

Technically, Plate B is still the maximum and the circulation of Plate C is somewhat restricted, but the frequency of excess-height rolling stock, at first ~18 ft (5.5 m) piggybacks and hicube boxcars then later autoracks, airplane parts cars as well as 20 ft 2 in (6.1 m) 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 ^[19].

The standard North American passenger railcar is 10 ft 6 in (3.2 m) wide by 14 ft 6 in (4.4 m) high and measures 85 ft 0 in (25.9 m) over coupler faces with 59 ft 6 in (18.1 m) bogie (truck) centers or 86 ft 0 in (26.2 m) over coupler faces with 60 ft 0 in (18.3 m) bogie (truck) centers. In the 1940s and 1950s, the American passenger car loading gauge was increased to a 16 ft 6 in (5.0 m) height in the West to accommodate dome cars and later Superliners and other double-decker trains.

References

External links

• EU High Speed Rail Rolling Stock Standards
• Berne and all that (1992 diagram of European loading gauges) at crowsnest.com (Diagrams do not show)
• 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
• UIC Leaflets