A control system with slow-in-turn capabilities for use with a self-propelled, steerable vehicle, such as a lawn mower, is disclosed. In one embodiment, the system slows the vehicle speed when turns are made beyond a predetermined range and the speed is at or above a predetermined level, as determined by a speed control device operatively connected to the speed control structure of a motive device by a speed control linkage. This slowing results in increased traction for achieving tighter turns and also improves dynamic stability. Two different types of rack-and-pinion steering systems capable of being used with the control system are also disclosed.