The generating factor of vibration, which occurred at the circumferential environment of a highway bridge, is the impact force produced by vehicles running the level difference of expansion joint. Such vibration has affected running stability, noise, infrasound and ground vibration. This study thought that reducing the impact force, at the time when vehicles are running the level difference of expansion joint, reduced the ground vibration. In the general case of the straight bridge, right and left rear wheels run on the expansion joint at the same time. However, in the skew bridge, rear wheel of either side do not run on the expansion joint at the same time. Therefore, the half impact force acting on the skew bridge is reduced. Then, the analytical models of extended deck bridges with various skew (80, 70 and 60 degrees) were made. The changes of the sound characteristics around the bridge were estimated by the dynamic response analysis due to running vehicles on the each analytical bridge model.
