The aging and structural degradation of a large number of civil infrastructures has contributed to significantly increase the interest in structural monitoring programs. The structural dynamics and traffic characterization of old metal bridges is a challenge for Civil Engineering, given the complexity and costs associated to the current monitoring process, particularly with regard to the high challenges and expenses involved in measuring the real responses of transport and energy infrastructures in the field. In this context, this article describes the evolution of static and dynamic parameters over one year of monitoring the Trezói Bridge, as well as the characterization of traffic on the Beira Alta railway line, after the bridge's rehabilitation process. This is done by using customized sensors which provide a monitoring system that overcomes the disadvantages of expensive classic solutions. The results obtained in this period highlight the robustness, effectiveness, autonomy and safety of using these customized sensors compared to traditional solutions. In addition, it is presenting a global perspective on the work that has been developed in this structure through all the instrumentation installed on the bridge.