Abstract
Several warning systems have been proposed as advanced vehicle safety devices using ITS technologies. To ensure effectiveness, warnings must be presented to the driver in a timely manner. When determining timing for appropriate output, we have to recognise the driver's reaction time to a warning indication. The purpose of this study is to clarify the driver's reaction time to the forward vehicle collision warning under several awareness conditions using a motion-based, full-scale driving simulator. This paper examines the factors that influence the reaction time after collision warning. The factors are the collision warning timing, the clearance to the preceding vehicle and the driver's awareness level.