A drive system for driving high-inertia loads such as, for example, conveyor belts for carrying minerals in mines, quarries, etc. The drive system for a high inertia load comprises a prime mover, a brake for holding the load stationary, reaction sensing means for indicating the reaction exerted by the brake on the load, a variable filling fluid coupling having its input connected to the prime mover and its output connected to the brake and load, the coupling having filling control means responsive to external control signals for starting and stopping the load, the control means being responsive to the brake reaction sensor and to the speed of the load in such a manner as, on receipt of a start-up signal, to release the brake under control such as to maintain a desired acceleration rate, and to start filling the fluid coupling such that the effect of such filling lags behind the restraining torque of the brake if the load is acting on it in the forward direction, but if the load is acting in the backward direction to maintain the brake engaged and cause the filling control means to increase the filling of the coupling until the drive torque exerted through the coupling reduces or eliminates the backward reaction sensed by the brake reaction sensor and thereafter to release the brake and progressively increase the coupling filling while monitoring the transmitted torque, until the working speed is attained, the control means being responsive to a stop signal to progressively reduce the coupling filling and to apply the brake while monitoring the torque exerted on the load to maintain it below a predetermined value.