Considering the emergency of pursuing the front car when a traffic signal is changing. The operation and behavior characteristics, such as response time, break pressure and stopping distance were quantificationally measured and analyzed between the passive driving of a car equipped with ACC (Adaptive Cruise Control) and the active driving of a car without ACC. According to the results, while there was a dependence between the speed and the headway distance in the active driving, it was not found in the passive driving, with respect to the response time. In the case of the time of break pressing, the results were reversed with respect to the response time. Furthermore, during passive driving, even at the emergent conditions, such as fast speed and short headway distance, the breaking pressure can achieve greater value in a shorter time.