Rail gauge

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Rail gauge

Rail gauge, sometimes track gauge, is the distance between the inner sides of the two parallel rails that make up a single railway line. Sixty percent of the world's railways use a standard gauge of 1,435 mm (4' 8½" in). Wider gauges are called broad gauge ; smaller gauges, narrow gauge. Break-of-gauge refers to a place where different gauges meet; sometimes this may involve transhipment and there may be extensive sheds to facilitate this. Some stretches of track are dual or mixed gauge, with three (or sometimes four) rails in place of the usual two, to allow trains of two or more different gauges to share the same path. Gauge conversion can be used to reduce break-of-gauge situations.

Comparison of the four different gauges common in India with UIC standard gauge which is not in railway use in India


  • BG - Broad Gauge
  • MG - Metre Gauge
  • NG - Narrow Gauge
  • SG - Standard Gauge


Broad Gauge (BG)

The first gauge used in India was one of 5' 6" (1676mm), settled upon in the belief that it offered greater stability in the face of Indian weather and the perceived threat of cyclonic winds, and offered economies in freight haulage.

Metre Gauge (MG)

In 1868, a decision was taken to permit the introduction of a smaller gauge in order to increase quickly the construction of railways in India. This decision was examined by the Gauge Committee set up by Government in 1869-70 - see sub-heading below.

Narrow Gauge (NG)

Later, two even narrower gauges (2' and 2' 6") were allowed to be used for feeder lines.

Standard Gauge(SG)

Although this 4 ft 8½ in (1,435 mm) gauge was the most usual throughout the world it was not adopted in India. There were a few exceptions:-

It is interesting to speculate how, in the 1920's when BG was becoming the norm, both the 'Bombay City Improvement Trust' and the 'Salsette Trombay Railway' came to use the Standard Gauge (SG)

Unique rail Gauges

The following have been identified (see individual pages for more information):-

Gauge conversion

Following the introduction of the metre gauge, the Government of India(GoI) occasionally allowed existing broad gauge lines to be converted to metre gauge and vice versa where expedient.


Despite four Commissions of Inquiry, the GoI did little te resolve the continuing problem of transhipment wherever there was a break-of-gauge.

Gauge Question

The content of this sub-heading is under construction.
The Government established The Gauge Committee in 1869 to examine the decision to allow metre gauge lines to be constructedand 1870 opposing views were put forward to Government

Project Unigauge

Starting about 1980, Indian Railways resolved to convert its legacy of metre and narrow gauge lines to broad gauge standards. This project is ongoing.