Abstract: A speed control mechanism for a hydrostatically driven vehicle such as a street sweeper is disclosed which includes a selector lever. When the lever is in a variable engine speed position, depression of an accelerator pedal progressively opens the engine throttle from idle speed to high engine speed and progressively closes an inching valve thereby enabling the operator to comfortably drive the vehicle through stop and go traffic. When the lever is in a governor controlled high speed position, the engine throttle is opened and the engine is driven at high speed under control of the governor, and progressive depression of the throttle progressively closes the inching valve thereby providing optimum power while the vehicle is working, such as sweeping streets, with the speed of the vehicle being controlled by the position of the throttle and the position of the inching valve.