A set of documents may be stored and indexed as a compressed sequence of tokens. The first cavity is in contact with the peripheral outer wall and the second cavity is arranged at a distance from the outer wall. When a point at which the curve degree is maximum is different from a point at which the deceleration value is maximum and also the point is located ahead of the vehicle, further necessary deceleration control is carried out. An Inverse Fast Fourier Transform is then applied to the component signals, which are sent to a processor. A reversible motor assembly is mounted to the flag pole and connected to the drive wheel.