DBR fitted on the roof of the Loco of WAP-4 /WAM -4 type Electric Locomotive in required to control a train of 1432 tonnes (24 Coach WAP/WAM hauled trains) on a continuous down gradient of 1 in 200 at a speed of 40 kmph and also to reduce the speed from its normal running speed 110/110 kmph to 40 kmph.