Overtrust and overreliance are dangerous driver states in driving support systems. These latent states are caused by the driver misunderstanding the performance of the system. To avoid overtrust and overreliance, and to achieve appropriate cooperation between a driver and a vehicle, the authors first investigate influence of an information feedback device. It naturally informs operation mode of a driving support system so that the vehicle achieves intuitive communication with the driver. The authors thus conduct an experiment using experimental Adaptive Cruise Control system to investigate influence of the information feedback device. The results indicates information feedback reduce driver's cognitive and operational workload.