This paper describes the structure of Adaptive Cruise Control (ACC) systems. To find out how driving with ACC systems will effect safety a simulation experiment was designed. To achieve the amount of realism needed this experiment uses a moving base driving simulator. During a 60 min. journey with an ACC vehicle and with an standard vehicle test subjects are exposed to several hazardous situations. Besides the subjective evaluation, done by psychologists, analysis of recorded data allows also to assess safety effects objectively.