Vehicle dynamics and the driver's behavior in emergent situations are the most important factors for the analysis of avoidance performance. However, the drivers' operations before traffic accidents have hardly been clarified.

In this study, the avoiding maneuver was examined by using a driving simulator to clarify the effects of the driver's age and vehicle characteristics. In the first test, the young or old driver's operation to avoid an emergent obstacle was investigated by using a driving simulator. The vehicle dynamics model in the driving simulator had two different vehicle characteristics. As a result, most drivers avoided the suddenly emerging obstacle only by braking action. In this case, old drivers delayed about 0.25 second in avoidance action compared with young drivers. It was derived that the driver of a vehicle with higher yaw velocity gain and less phase delay had less deviations from the road than the driver of the other vehicle with different characteristics. The second test using a driving simulator was done to investigate the drivers' maneuver in the emergent change of the road surface friction coefficient. All drivers steer vehicles to decrease the yaw-rate and the slip angle. However, most drivers cannot restrain the vehicle instability.

These two kinds of experimental conditions and the driver's operation values have been collected to construct a database system. This database system searches for the driver's operation value according to the conditions, and the searched data are obtained as a graphical image plot.
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