Tuned rotary damped mass damper (TRMD) is a new kind of passive vibration control system which consists of a rolling mass and container allowing free movement of the mass along its inner arc. This system can reduce the vibration of the structure by using the control power generated by the rolling movement of the mass. The tuning of the natural frequency of TRMD can be made by adjustment of the diameter of the mass and the curvature inside the container. In order to verify the effectiveness of TRMD, it is applied to a vibrating lamppost on a highway bridge. As a result of the application of TRMD, the vibration of the lamppost was significantly reduced. We also measured the stress near the base of the lamppost to demonstrate that the reduction of fatigue stress by TRMD elongates the life of the lamppost. Morio Obata, BS, MS Dept of Civil Engineering, Tokai University, on Subbatical from the Technical Research and Development Center, Nippon COMSYS Corporation, Japan Yoji Shimazaki, BS, MS, PhD, Dr eng Professor, Department of Civil Engineering, Tokai University, Japan