Loading gauge

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.

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.

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.

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.

Rapid transit (metro) railways generally have a very small loading gauge, which reduces the cost of tunnel construction.

In mainland Europe, the slightly larger Berne gauge (Gabarit passe-partout international, PPI) was agreed to in 1913 and came into force in 1914.

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.

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 4,303 millimetres (14 ft 1+3⁄8 in) high,[14] the Netherlands, Belgium and Switzerland feature large numbers of double decker intercity trains as well.

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 2.44 m (8 ft 0 in) ISO containers, and the W8 loading gauge has an even larger notch spanning outside of the curve to accommodate the transport of 2.6 m (8 ft 6 in) ISO containers.

[15] 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).

Some modern electric multiple units, like Regina X50 with derivatives, are somewhat wider than normally permitted by SE-A at 3.45 m (11 ft 4 in).

[30] The most widespread standards are AAR Plate B and AAR Plate C,[31] 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.

[30][31] All the Class I rail companies have invested in longterm projects to increase clearances to allow double stack freight.

The structure gauge of the Mount Royal Tunnel used to limit the height of bilevel cars to 14 feet 6 inches (4.42 m) before it was permanently closed to interchange rail traffic prior to its conversion for the REM rapid transit system.

[citation needed] 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.

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.

[41] 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.

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 3,400 mm (11 ft 2 in) maximum width and can accept the maximum height of 4,500 mm (14 ft 9 in).

[44] 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".

[citation needed] The Commonwealth Railways adopted the national standard of 10 ft 6 in (3.20 m) when they were established in 1912, although no connection with New South Wales was made until 1970.

[55] It was accepted by the Interstate Council for Standardization, Metrology and Certification to be valid in Russia, Belarus, Moldova, Ukraine, Uzbekistan and Armenia.

The static profile 1-T is the common standard on the complete 1520 mm rail network including the CIS and Baltic states.

For international traffic, the standard references the kinematic envelope for GC and defines a modified GCru for its high-speed trains.

The profile Tpr has the same lower frame requirement but reduces the maximum upper body width to 3,500 mm (11 ft 5+13⁄16 in).

By comparison, several standard gauge 73 class locomotives of the NSWR, which are 9 feet 3 inches (2.82 m) wide, have been converted for use on 610 mm (2 ft) cane tramways, where there are no narrow bridges, tunnels or track centres to cause trouble.

Translation of legend: The Japanese national network operated by Japan Railways Group employs narrow gauge 1,067 mm (3 ft 6 in).

The maximum allowed width of the rolling stock is 3,000 mm (9 ft 10 in) and maximum height is 4,100 mm (13 ft 5 in); 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.

Analysis showed that the properly configured train would have passed safely even though the platform couldn't handle the maximum design sway of W6a.