By going back to basics, we first consider “What is comfort?” Among them, this chapter will focus on “vibration-free railcars.” Its key player is the suspension, and its design policy is soft. The skier's graceful movements on uneven snow surfaces are a reminder of this. The knee joints are softened so that the effect of unevenness is not transmitted to the upper body by folding and stretching the legs. However, if they are made too soft, various problems arise, such as the height of the car body changing depending on the number of passengers. The solution to this problem is the air spring. In Japan, it was introduced early in the railway. Since steel wheels cannot be used as springs as in automobile tires, axle springs are adopted to provide a two-stage suspension with excellent anti-vibration performance. In addition, some railcars adopt active suspension, a key to improving ride comfort. Improvements in the track structure and the rail maintenance methods, as well as the introduction of the continuous welded rail with no rail joints, have also contributed to the cars being vibration-free.