Vehicle safety is an urgent problem for decreasing traffic accidents. Almost all the causes of the accidents are related with human factors in driver's maneuvers; recognition, judgement and operation. Improving the active safety performance of vehicles as well as basic motion stability and controllability becomes more important for ordinary drivers. It is indispensable to discuss from the viewpoints of the vehicle performance and driver's behavior.
In this study, taking the driver-vehicle closed loop system into account, the active safety performances in emergent situations were analyzed, and evaluation methods were proposed. Under such a critical condition, ordinary driver's driving performances were examined using a motion-type driving simulator. According to the driver's maneuvers, a database of driving operations under various emergent conditions was constructed, and a mathematical model of driver's operation was also derived from the database. The performance of the driver-vehicle system was predicted by computer simulations. The agreements between the maneuver predicted by the simulation and the experimental result obtained using the driving simulator were verified from the results in emergent situations. Supposing the sudden change of the road surface to a slippery situation, the effect of assistant control of steering was also estimated from both of the model simulation and experiment using a driving simulator.