A speed controller's primary input, for an internal combustion engine-based vehicle, is the throttle angle. The most common way to adjust the throttle angle setting is with a pneumatic actuator. When a faster and more accurate throttle response is desired, the pneumatic based system is generally replaced with a stepping motor mounted directly on the throttle plate assembly. For controller design purposes that fit the physical situation, a model of the throttle actuator system has been developed that is comprised of two second-order linear systems. Using this variable structure model, a switching controller has been designed which has been verified, both theoretically and experimentally, to work satisfactorily. This paper provides an interesting example of designing a reference tracking controller for a real physical system by switching between its stable and unstable structures while achieving closed loop stability.