Collision warning and collision avoidance systems are emerging automotive safety technologies that assist drivers in avoiding rear-end collisions. Their function is to allow the driver enough time to avoid the crash and yet avoid annoying the driver with alerts perceived as occurring too early or unnecessary. The aim of this paper was analyzing the driver's behavior in order to define effective driver assistance systems which can be readily accepted by the driver. A study was performed with an

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... nteractive fixed-base driving simulator. A sample of 32 drivers drove on a two-lane rural road. Four different driving traffic conditions were implemented. The data recorded during the tests were analyzed to assess the safety distances required by the driver during a carfollowing situation. Based on the risk perception of the driver a new collision warning algorithm was developed.