The fundamental problem in the study of vehicle mobility is the development of traction between the vehicle and the supporting terrain. The mechanics of energy transfer will essentially control the final performance of the surficial machine. Determining and predicting the capability of a particular piece of machinery to traverse successfully a specific piece of terrain is very complex, particularly as the characteristics and properties of different types of terrain cover vary considerably, as do the many types of vehicle and their running gear. The material that forms the basis of this book has been gathered over many years of study both in the laboratory and in the field. It studies vehicle traction mechanics from the viewpoint of the interaction between the vehicle and the ground surface. The types of machines covered include earth-moving, forestry, agricultural, and construction machines. In addition, the mechanisms involved in the development of traction and the working of the terrain through cultivation, construction and surface disturbances are examined. The book also addresses the problems of off-road mobility and terrain trafficability, especially from the terrain-support and terrain interaction points of view. It is the authors" aim that the book will provide the reader with the ability to both analyze and predict the traction capability of his proposed machinery, and also to anticipate the kinds of reactions that will occur in the ground and at the ground surface.