Prior to Independence whole of the railway network was under steam traction. Since it had poor efficiency, caused more environmental pollution and consumed more coal it was decided to replace it by diesel and electric tractions.
Consequently, new locomotives were set up to manufacture diesel and electric engines and electrify railway tracts. At present Diesel Locomotive Works (DLW), Varanasi; Chittaranjan Locomotive Works, Mihijam; and Tata Engineering and Locomotive Works, Jamshedpur are busy in the manufacture of such locomotives.
Dieselisation was adopted in the Indian railways to speed up train services and to check environmental pollution by steam locomotives. Due to concerted efforts the number of diesel locomotives increased to4, 769 in 2003-04 against 1,169 in 1970- 71 and 17 in 1950-51.
Electric traction is even better than diesel inaction because it is more capital intensive, and environment friendly. It leads to speeding up the trains and intensive use of the railway track so as to bring down the running cost.
In 1950-51 only 388 kms of route and 937 kms of the running route were electrified. By 1980-81 the total length of electrified route rose to 5,345 km. In 2003-04 the total electrified route length was 17,503 km accounting for 27.69 percent of the total route length of the railways. Similarly the number of electric locomotives used by the Indian railways increased from 72 in 1950-51 to 1,036 in 1980-81 and 3,003 in 2003-04 exhibiting about 42 times growth during the last 53 years.
In electrification priority has been given to high density sections of the rail lines. Some important electrified tracks are: Haora-Delhi, Mumbai- Jalgaon, Mumbai-Pune, Haora-Bilaspur, Delhi- Mumbai, Delhi-Chennai, Ahmadabad-Surat, Chennai-Villupuram, Igatpuri-Bhusaval, Rourkela- Birmitrapur, Mumbai-Suburban areas, and Chennai Suburban areas. During Ninth Five Year Plan Railways have planned electrification of 2300 route km. currently electrification work is in progress in Erode- Ernakulam, Adra-Medinipur, Kanpur-Lucknow and Krishnanagar-Lalgoia sections of the rail line.