WDM 1 
W- Broad gauge
D- Diesel
M- Mixed(For both freight and passenger)

The first class of WDM locomotives were used for hauling both freight and passenger trains. These are the first mainline diesel engines imported after Independence. They were even the fastest diesel locomotives till the advent of WDM 2 and WDM 4. They used to haul ore/freight trains on SER. In the end they were relegated to shunting/piloting duty or hauling sugarcane freight trains. One unit is preserved at National Rail Museum, Delhi. These locomotives were made by ALCO during the years 1957-59. A total of 100 locomotives of this kind were produced during this period. These locomotives used 12 cylinder four stroke engines. It had a maximum speed of 104kmph (65mph) and its rated speed was about 100kmph (62mph).