This research is related to the study of the reinforced concrete arch Arrábida Bridge with the purpose of benefiting from new solutions of measurement systems in the Structural Health Monitoring of bridges, owing to the increasing importance of the continuous monitoring of Civil Structures. The instrumentation was implemented with the installa-tion of accelerometers, displacement sensors and strain gauges. Through the measure-ments obtained with the accelerometers, it was possible to identify the modal proprieties of the bridge such as natural frequencies and damping factors using the SSI-Cov meth-od and a Cluster Analysis, allowing the evaluation of the evolution of these properties for long periods. The displacements registered in the expansion joints permitted to iden-tify a dynamic component and the analysis of these signals in parallel with the mid-span vertical displacement and strain gauges at the longitudinal beams of the bridge allowed estimating the traffic loads over the deck.