In a diesel-hydraulic multiple unit, a hydraulic torque converter, a type of fluid coupling, acts as the transmission medium for the motive power of the diesel engine to turn the wheels. Some units feature a hybrid mix of hydraulic and mechanical transmissions, usually reverting to the latter at higher operating speeds as this decreases engine RPM and noise.

This Moula Ali based DHMU, serving Secunderabad - Medchal route, was negotating a curve at Lallaguda Gate station when framed by Roy on 21st March 2011.