Driving fatigue demonstrates itself in many ways. This paper focuses on the cau ses, process and mechanism leading to driving fatigue and its effects on driving . It narrates the assessment and field test of the driving fatigue. It covers th e following: 1. Mathematic models are made to indicate the function of each factor, direct a nd indirect, and the interaction between individual factors that cause driving f atigue, based on in-depth study of driving behavior. 2. By using transfer function, the paper analyses driving fatigue in a quantiti ed, intensitied and modular way. Based on automatic control theory, driving fati gue is analogized as two parts: inertia and proportion differential. The result shows that the driving fatigue has the general characteristics of two-order sys tem. 3. According to the reliability theory, the paper discusses the compressive eff e ct of driving fatigue factors including their characteristics of fuzziness, rand omicity and interaction. As a result, the variables of the driving fatigue is a restriction condition, which is related to time factor, its relaxation character istic is obvious. While driving fatigue is assessed from the view of men-machin e-environment system, the value of driving fatigue factors are calculated. 4. The paper divides the work into five modes: muscle, sensation, information p rocessing, thinking and creativity modes, with their constituent components. Dri ving fatigue behaviour is mainly composed of the sensation and the operation fat igues. Therefore, a new concept of the driving fatigue formation, accumulation a nd variation is discussed in-depth. 5. Driving fatigue equilibrium testing system produced by our lab is applied in the research. It examines the driving fatigue by tracing the track of the cente r of gravity, which reflects the respective and cooperative capability of sensat ion, center and motor nerve system. Once the driving fatigue occurs, the driver will loose his balance due to the reduction of the above-mentioned capability. Based upon a gr
