Broad gauge: Encyclopedia - Broad gauge

Broad gauge

Broad gauge railways use a rail gauge (distance between the rails) greater than the standard gauge of 4 ft 8½ in (1435 mm).

In Britain the Great Western Railway designed by Isambard Kingdom Brunel pioneered broad gauge from 1838 with a gauge of 7 ft 0¼ in (2140 mm), and retained this gauge until 1892.

While the parliament initially supported the broad gauge, it was eventually rejected by the Gauge Commission in favour of all railways being built to Standard Gauge for compatibility. Parliament was more concerned at this time about making profits rather than improving railway conditions. Broad gauge lines were gradually converted to dual gauge or standard gauge from 1864, and finally the last of Brunel's broad gauge was converted in 1892.

Many countries have broad gauge railways. Ireland (see History of rail transport in Ireland) and some parts of Australia have a gauge of 5 ft 3 in (1600 mm). Russia and the other former Soviet Republics use a 1520 mm (originally 5 ft (1524 mm)) gauge while Finland continues to use the 5 ft (1524 mm) gauge inherited from Imperial Russia (the two standards are close enough to allow full interoperability between Finland and Russia). The Baltic States have received funding from the European Union for rebuilding their railways to the standard gauge. Portugal and the Spanish Renfe system use a gauge of 5 ft 5½ in (1668 mm). In India a gauge of 5 ft 6 in (1676 mm) is widespread. This is also used by the Bay Area Rapid Transit (BART) system of the San Francisco Bay Area. In Toronto, Canada the TTC subways and streetcars use a unique gauge of 4 feet 10 7/8 inches (1495 mm), an "overgauge" originally intended to allow standard gauge horse-drawn wagons to run inside the rails while the streetcars ran on top of them.

While Russia chose broad gauge to make railborne invasion by its enemies that much more difficult, most non-standard broad gauges get in the way of interoperability of railway networks. On the GWR, the 7 ft 0.25 in (2140 mm) gauge was supposed to allow for high speed, but the company had difficulty with locomotive design in the early years (which threw away much of their advantage), and rapid advances in permanent way and suspension technology saw standard gauge speeds approach broad gauge speeds within a decade or two in any case. On the 5 ft 3 in (1600 mm) and 5 ft 6 in (1676 mm) gauges, the extra width allowed for bigger inside cylinders and greater power, a problem solvable by outside cylinders and higher steam pressure on standard gauge. On BART, the wider gauge is supposed to prevent lightweight trains from being blown over by the wind.

Broad gauge - Overcoming a break of gauge

Where trains encounter a different gauge (a break-of-gauge), such as at the Spanish-French border or the Russian-Chinese one, the traditional solution has always been transshipment - transferring passengers and freight to cars on the other system. This is obviously far from optimal, and a number of more efficient schemes have been devised. One common one is to build cars to the smaller of the two systems' loading gauges with bogies that are easily removed and replaced, with switching of the bogies at an interchange location on the border. This takes a few minutes per car, but is quicker than transshipment. A more modern and sophisticated method is to have multigauge bogies whose wheels can be moved inward and outward. Normally they are locked in place, but special equipment at the border unlocks the wheels and pushes them inward or outward to the new gauge, relocking the wheels when done. This can be done as the train moves slowly over special equipment.

In some cases, breaks of gauge are avoided by installing dual gauge track, either permanently or as part of a changeover process to a single gauge.

Broad gauge - Broader gauges

Some applications for railways require broader gauges, including:

• Telescopes
• Rocket launchers
• Ship railways

These applications might use double track of the country's usual gauge to provide the necessary stability and axle load.

Broad gauge - Specific names

• Ohio gauge - 4 ft 10 in, used in Ohio, USA
• Provincial gauge - 5 ft 6 in, used in Ontario, Canada to prevent use by enemy forces invading from the U.S.

See also

• Breitspurbahn
• Standard gauge
• Narrow gauge

Category: Rail transport

Adapted from the Wikipedia article "Broad gauge", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki