This paper describes the evaluation of brake assistance system. A new brake assistance system based on driver's operation was proposed previous work. Previous work took note of the characteristics of gas pedal operation. This system based on experimental results which were experiment with test car and driving simulator. But such brake assistance system was not verified in real road traffic. So this study intends to validation such brake assistance system in real road traffic. But in real road traffic, we cannot set this brake assistance system by the traffic law. In consequence, this study intends to prove that evaluation value of this system does not over the threshold at usually driving.