Meter Gauge, though rare gauge today, used to be the dominant gauge at that time.
The Class YDM4 was a Indian Railways' workhorse diesel locomotive.
The first units were imported fully built from the American Locomotive Company (AlCo) in 1961.
Since 1968, it has been manufactured in India by the Diesel Locomotive Works (DLW), Varanasi.
The model name stands for Meter Gauge/Yard Gauge (Y), Diesel (D), Mixed Traffic (M) Locomotive.
The YDM4 have been the most successful Diesel Locomotive in the Meter Gauge operation of Indian Railways.
From 1969 till 1993 DLW produced YDM4 locomotives for the Indian Railways.
