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.
- 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.
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:-
- Yamuna River, Okhla Canal Construction Tramway used from 1869 to 1874 to build the headworks from the Yamuna River at Okhla. It was Standard Gauge tramway used to carry stone.
- Calcutta Tramways Company adopted the Standard Gauge on its electric tramcars from 1900 onwards, on conversion from the MG horse drawn tram system.
- Bombay City Improvement Trust Railways The records show a total of twenty-one standard gauge (SG) locomotives dating from 1920-23 that were supplied to the Bombay City Improvement Trust Schemes. The destiny of these locomotives on completion of the schemes in the mid 1920's is unknown.
- Salsette Trombay Railway The records show that eight SG locomotives dating from 1921-22 were supplied for the 'Salsette Trombay Railway' which did not commence operations until 1928.
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):-
- Salkhia Salt Depot Tramway used a 3ft 0t½ inches (927cm) gauge for a hand-worked tramway from 1861-62
- Akra Brick Factory Tramway used a 4ft(1222cm) gauge from mid 1860's connect the factory with the jetty
- Nalhati-Azimganj Railway, the original name for the Indian Branch Railway; constructed in 1863 used a 4ft(1222cm) gauge, later converted to BG.
- Sone Canal Construction Railway/Tramway used a 4ft(1222cm) gauge during the construction 1868-74*Arakkonam-Conjeevaram Tramway, absorbed into the Indian Tramway Co. was a 3'6"(1067mm) gauge line which opened in 1865, converted in 1878 to MG.
- Karachi Tramway used a 4ft(1222cm) gauge for its city tramway from its horse drawn opening in 1865, steam powered from 1886 and petrol driven from 1912-15 until closure in 1975
- Chirimiri Colliery Railway used a 3ft 0in(915mm) gauge locomotives operational from 1932.
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.
Over the years there were various views, proposals and recommendations regarding the choice of Rail Gauge throughout India.
The following is mainly extracted from the 1870-71 Report on Railways’ transcribed by Fibis see separate page with the relevant Paragraphs as referenced
1859 The Broad Gauge of 5 feet 6 inches was fixed upon when Indian railways were first commenced in the year 1859. Lord Dalhousie (founder of the Public Works Department) was in favour of 6 feet; but after much consideration 5 feet 6 inches was decided upon as preferable .
1862-66 The introduction of a lighter system of railways into India was more than once proposed. Colonel Henry Yule R.E., C.B. with the Indian Branch Railway Company constructed two short lines of lighter construction (the Nalhati-Azimganj Railway and the Cawnpore-Lucknow-Fyzabad Railway) both with James E Wilson being their engineer .
1869 The recommendation that a much narrower gauge than 5 feet 6 inches should be applied to future lines of railway in India was made by the Viceroy Lord Mayo with the chief ground upon being that of economy. He and the members of his Council considered that the railway system of India was really in its infancy and that such saving could be most satisfactorily secured by adopting a narrow gauge. The Government of India regarded 3 feet 6 inches as the maximum that should be used but begged that this point should be determined in England .
1870 “Gauge Committee” formed, consisting of Colonel R. Strachey, R. E., C.S.I., Colonel C. H. Dickens, R.A., C. S. l., Mr. John Fowler, C.E., and Mr. A. M. Rendel, Consulting Engineer to the East Indian Railway Company, was accordingly appointed "to consider the precise gauge and general character for an average narrow gauge line of railway in India." The result of their investigations and deliberations was given in two reports, one containing the conclusions at which all the members of the committee, excepting Mr. Fowler, had arrived, the other expressing that gentleman's opinion alone. All, including Mr. Fowler, were in Favour on the ground of economy, of introducing a narrower gauge into India than the present standard of 5 feet 6 inches in districts where a break of gauge would not be productive of serious inconvenience, but they differed as to what that gauge should be. Colonel Strachey, Colonel Dickens, and Mr. Rendel recommended 2 feet 9 inches; Mr. Fowler, 3 feet 6 inches. .
1870 Lord Mayo engaged an American engineer to advise him. It was decided that less productive areas such as Rajputana and the Punjab should be opened up by narrower gauge railways, which would be more suited than the broad gauge to handle the limited traffic expected. Mayo himself decided which of the narrow gauges should be adopted. Narrow-gauge enthusiasts were divided between supporters of a 3ft 6in gauge, which had been chosen for lines in other British territories, and 2ft 9in, which was cheaper and quite adequate for the expected traffic. Mayo rejected 2ft 9in because this gauge was untried elsewhere, and because cavalry horses could not travel two abreast on a 2ft 9in gauge vehicle. He compromised by favouring 3ft 3in. But as he was at that time planning to introduce the metric system into India, he decided that metre gauge was preferable. Hence the 3 feet 3⅜ inches in choice; but 80 more years were to pass before the metric system was introduced generally 
1871-74 A battle of the gauges began almost immediately. Some of the railways intended to be built on the metre gauge had a strategic significance, especially the Indus valley and Peshawar lines. The Commander-in-Chief objected that this would mean time-consuming transhipment of troops and stores en route to any possible emergency on the NW frontier. Later he agreed that a metre-gauge line was better, from the military point of view, than no line at all. When objections were raised, however, in the House of Commons to this gauge policy, the C-in-C reverted to his original opposition and demanded broad-gauge tracks for these lines .
The implications of the consequential break of gauges is clearly examined in the chapter ‘Break of Gauge’ in a 1930 work ‘Development Of Indian Railways’ by Nalinaksha Sanyal available as a on-line pdf, and as a text version .
1879 January Government rescinded its previous order and on various grounds of economy, military considerations and convenience of working decided to construct the whole of the Rajputana-Malwa line on the metre gauge. The decision however was to revert to the 5 feet 6 inches broad gauge(BG) for all new constructions .
Starting about 1980, Indian Railways resolved to convert its legacy of metre and narrow gauge lines to broad gauge standards. This project is ongoing.
- ‘1870-71 Report on Railways’ para.11 transcribed by Fibis see separate page
- ‘1870-71 Report on Railways’ para.12 transcribed by Fibis see separate page
- Railways of India by J. N. Westwood. 1974. David and Charles London quoted with permission
- ‘Break of Gauge’ extracted from “Development Of Indian Railways” by Nalinaksha Sanyal, University of Calcutta, Calcutta. Publication date 1930. Chapter vii, pages 91, pdf 106 citing Despatch, dated 10th January 1871; Retrieved 20 Mar 2020
- ‘Break of Gauge’ extracted from ‘Development Of Indian Railways’ by Nalinaksha Sanyal, University of Calcutta, Calcutta. Publication date 1930. Chapter vii, pdf version pdf 103-111 ; Retrieved 20 Mar 2020
- ‘Break of Gauge’ extracted from ‘Development Of Indian Railways’ by Nalinaksha Sanyal, University of Calcutta, Calcutta. Publication date 1930. Chapter vii, text version pages 88-96; Retrieved 20 Mar 2020
- ‘Break of Gauge’ extracted from “Development Of Indian Railways” by Nalinaksha Sanyal, University of Calcutta, Calcutta. Publication date 1930. Chapter vii, pages 91, pdf 106 citing Despatch No. 24 Railway, dated 24th Januaiy 1879; Retrieved 20 Mar 2020