The Indian locomotive class WDM-3D is a class of diesel-electric locomotive that was developed in 2003 by Banaras Locomotive Works (BLW), Varanasi for Indian Railways. The model name stands for broad gauge (W), Diesel (D), Mixed traffic (M) engine with 3300 horsepower (3D). The engine is classified WDM-3D though it outputs only 3300 hp and not 3400 hp as the name should suggest. They entered service in 2003. A total of 590+ WDM-3D were built at Banaras Locomotive Works (BLW), Varanasi between 2003 and 2016. The WDM-3D is one of the most successful locomotives of Indian Railways serving both passenger and freight trains. A few WDM-3D units were exported or gifted to neighboring countries like Sri Lanka and Bangladesh. A significant number of these locomotives are still in use, both on mainline and departmental duties. As of October 2021, most of the locomotives still retain "operational status" on the mainline as WDM-3D, with further examples having been converted from WDM-3B. History WDM-3D was developed in by Banaras Locomotive Works and Research Design and Standards Organisation in 2003. It was the result of DLW integrating the best features of EMD GT46MAC and EMD GT46PAC with the ALCO platform. The first one was built in July, 2003, numbered #11101. The first few units (five) were all homed at krishnarajapuram but were later transferred to Erode. Serial production started in late 2005 with locos being allotted to almost all major BG diesel sheds. Earlier WDM-3Ds had issues with their electronics which probably led to the development of the WDM-3B in 2005, the same WDM-3D without microprocessor control. The class is considered successful with over 590 units being built. The production has now ceased as DLW has moved to manufacturing more Advanced locos. One unit #11121 has a modified short hood, similar to WDP-4 and is homed at Erode. Specification It is the higher-powered version of the Indian locomotive class WDM-3A. These locos have a 3300 hp power pack, with maximum available traction power of 2925 hp. The engine is an enhanced version of the 16-cylinder Alco 251C model with a max. speed of 160 km/h. The bogies are Improved Fabricated (welded) Alco High-Adhesion Co-Co bogies with stem type vertical and lateral dampers in place of 'eye' type which helps reduce wheel slip and maintenance. The loco features left hand drive, WDG-3A style High Adhesion bogies, air cylinder under foot-board, WDP-4 style fuel tanks,