The authors have proposed a driving assistant system which is referred to as PRE3 (prediction by pre-preceding vehicle) and confirmed through a driving simulator (DS) and a traffic simulator (TS) experiments that it is efficient for the following driver to anticipate the pre-preceding vehicle in order to make the platoon stable. This paper evaluated the ability of the PRE3 for stabilizing the shockwave (SW) that propagates backward the 3-vehicle platoon. Numerical analyses based on the shockwave theory showed that the PRE3 helps to reduce the generation of SW backpropagation, alleviate the SW speed and minimize the deviation of car-following states among the platooned vehicles. Also, the PRE3 makes the time headway increased more from the brake initiation until the SW speed is maximized. It was concluded that PRE3 is significantly efficient in alleviating the shockwave backpropagation and avoiding the risk of rear-end collision when decelerating.