Major aspects of engineering planetary transportation vehicles are discussed. Emphasis is placed on the the mechanics of mobility and mobility system design, including considerations for designing the wheels, drive, steering, and suspension systems. Because mobility performance of any vehicle is extremely sensitive to environmental (e.g. soil properties) and design (e.g. vehicle weight) parameters, the mechanics of mobility are addressed by parametric application as well as empirical (derived relationships and equations) form. Finally, and more philosophical in nature, discussions of the key considerations for designing and analyzing each of the components of mobility (locomotion, steering, suspension, and stability) are also included. These discussions include some general guidelines to assist in determining the values of key design parameters.