The countermeasures to ground vibrations generated by car traffic are summarized and among them the detail of the soft ground improvement is described. The field tests and the finite element analyses were performed on the reduction of ground vibrations of soft ground improvement. At the field tests the ground was improved at a region of 20m in width, 30 m in length and 12 m in depth by the lime pile method and the ground vibration test was conducted by using a vibration generator.