This paper describes analytical and experimental methods used to ensure a maximum amount of safety in the design of a high-speed snowmobile. Constructional features of the resultant record-breaking 140 mph snowmobile Pegasus are related to the various specifications considered essential to operator safety. Development of this vehicle involved investigation of crucial parameters such as yaw and drag on directional stability while operating at high speeds. These effects and other aerodynamic influences are explained as they affect single-track and dual-track vehicles. The final design of this snowmobile incorporated measures to counter adverse tendencies during high-speed operation, as well as backup devices such as a rollover bar, auxiliary braking system, fire protection, and an escape mechanism.