As the name suggests, you have seen this coding in front of many trains. So lets discuss! Firstly, W stands for Wide gauge, D stands for Diesel engine & M stands for mixed (the engines which are capable of pulling both passenger coaches and frieght). Lets start with the first engine WDM 1. 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 duties or hauling sugarcane freight trains. One unit is preserved at National Rail Museum, Delhi. This was manufactured by ALCO (American Locomotive Company). About 100 engines were produced in the years between 1957 to 1959. They have a max speed of 104 kmph
