Project Unigauge-Comparison of gauges in India with the standard gauge

Project Unigauge, started on 1 April 1992, is an ongoing effort by Indian Railways to convert and unify all rail gauges in India to 1,676 mm (5 ft 6 in) broad gauge.

Project Unigauge-Comparison of gauges in India with the standard gauge
Comparision of Railway Track Guages in Project Unigauge India

Project Unigauge started on 1 April 1992, is an ongoing effort by Indian Railways to convert and unify all rail gauges in India to 1,676 mm (5 ft 6 in) broad gauge.

Lines which are preserved / will not be converted.

  • Darjeeling Himalayan Railway (NG)
  • Nilgiri Mountain Railway (MG)
  • Kalka–Shimla Railway (NG)
  • Matheran Hill Railway (NG)
  • Kangra Valley Railway (NG)
  • Marwar Jn – Ghoram Ghat (MG)

Standard-gauge railway

A standard-gauge railway has a track gauge of 1,435 mm (4 ft 8+1⁄2 in). The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, standard gauge and European gauge in Europe, and SGR in East Africa. It is the most widely used railway track gauge around the world, with approximately 55% of the lines in the world using it.

All high-speed rail lines use standard gauges except those in Russia, Finland, and Uzbekistan. The distance between the inside edges of the rails is defined to be 1435 mm except in the United States and on some heritage British lines, where it is described in U.S. customary/ Imperial units as exactly "four feet eight and one-half inches" which is equivalent to 1435.1 mm.

Break of gauge

With railways, a break of gauge occurs where a line of one track gauge (the distance between the rails, or between the wheels of trains designed to run on those rails) meets a line of a different gauge. Trains and rolling stock generally cannot run through without some form of conversion between gauges, leading to passengers having to change trains and freight requiring transloading or transshipping; this can add delays, costs, and inconvenience to travel on such a route.

Types breaks of gauge

Minor breaks of gauge: - Wherever there are narrow-gauge lines that connect with a standard-gauge line, there is technically a break of gauge. If the amount of traffic transferred between lines is small, this might be a small inconvenience only. In Austria and Switzerland, there are numerous breaks of gauge between standard-gauge main lines and narrow-gauge railways.

Many internal Swiss railways that operate in the more mountainous regions are 1,000 mm (3 ft 3+3⁄8 in) metre gauge, and most are equipped with rack assistance to deal with the relatively steep gradients encountered. Through the running of standard-gauge trains on the rack, sections would not be possible, but dual-gauge track exists in many places where the gradient is relatively flat to carry standard- and metre-gauge stock. There are also some 800-mm-gauge railways which are entirely rack operated.

The effects of a minor break of the gauge can be minimized by placing it at the point where cargo must be removed from cars anyway. An example of this is the East Broad Top Railroad in the US, which had a coal wash and preparation plant at its break of gauge in Mount Union, Pennsylvania. The coal was unloaded from narrow-gauge cars of the EBTR, and after processing was loaded into standard-gauge cars of the Pennsylvania Railroad.

Nominal breaks of gauge

The line between Finland and Russia has a nominal break of gauge; the Finnish gauge is 1,524 mm (5 ft) whereas the Russian gauge is 1,520 mm (4 ft 11+27⁄32 in); the present Russian gauge is actually a redefinition of the older 1,524 mm (5 ft).

This does not usually prevent through-running - service running across both gauges exists in the form of the Allegro high-speed service between Helsinki and St. Petersburg. The nominal 4 mm (0.16 in) difference is generally within operating tolerances and does not cause problems or delays.

The Iberian gauge is actually three slightly different gauges: 1,672 mm (5 ft 5+13⁄16 in) in Spain, 1,664 mm (5 ft 5+1⁄2 in) in Portugal, and the newer, redefined 1,668 mm (5 ft 5+21⁄32 in). Through-running is done with vehicles having a gauge within certain tolerances.

Indian gauge, 1,676 mm (5 ft 6 in), is also compatible with Iberian gauge, although there are no actual railway connections between the two. Despite this, old Spanish and Portuguese rolling stock have been reused in Argentina and Chile, both of which use Indian gauge.

A nominal break of gauge with standard gauge exists as well: on the Hong Kong MTR network, lines owned by MTR Corporation used 1,432 mm (4 ft 8+3⁄8 in) before 2014. Newer lines and extensions use 1,435 mm (4 ft 8+1⁄2 in) with nominal gauge break at Sheung Wan station and Yau Ma Tei station.

1,435 mm (4 ft 8+1⁄2 in) is also employed on those owned by KCR Corporation, despite the lack of physical connections between the two networks.

Other types of breaks

A large railway may have main lines with heavy tracks, and branch lines with the light track. Light locomotives and rolling stock can operate on all lines, but heavy locomotives and rolling stock can only operate on the heavy track. The heavy rolling stock might be able to operate on a lighter track at reduced speed. The light track can be upgraded to a heavy track by installing heavy rails, etc., and this can be done without changing the track gauge.