Indian locomotives

The locomotives of India presently consist of electric and diesel locomotives. Steam locomotives are no longer used in India, except in heritage trains. A locomotive is also called loco or engine.

The Bengal Sappers of the Indian Army were the first to run a steam locomotive in India. The steam locomotive named Thomason ran with two wagons for carrying earth from Roorkee to Piran Kaliyar in 1851, two years before the first passenger train ran from Bombay to Thane in 1853.

In India, locomotives are classified according to their track gauge, motive power, the work they are suited for and their power or model number. The class name includes this information about the locomotive. It comprises 4 or 5 letters. The first letter denotes the track gauge. The second letter denotes their motive power (Diesel or Electric) and the third letter denotes the kind of traffic for which they are suited (goods, passenger, mixed or shunting). The fourth letter used to denote locomotives' chronological model number. However, from 2002 a new classification scheme has been adopted. Under this system, for newer diesel locomotives, the fourth letter will denote their horsepower range. Electric locomotives don't come under this scheme and even all diesel locos are not covered. For them this letter denotes their model number as usual.

A locomotive may sometimes have a fifth letter in its name which generally denotes a technical variant or subclass or subtype. This fifth letter indicates some smaller variation in the basic model or series, perhaps different motors, or a different manufacturer. With the new scheme for classifying diesel locomotives (as mentioned above) the fifth item is a letter that further refines the horsepower indication in 100 hp increments: 'A' for 100 hp, 'B' for 200 hp, 'C' for 300 hp, etc. So in this scheme, a WDP-3A refers to a 3,100 hp (2,300 kW) loco, while a WDM-3F would be a 3,600 hp (2,700 kW) loco.

Note: This classification system does not apply to steam locomotives in India as they have become non-functional now. They retained their original class names such as M class or WP class.

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Wikipedia