In seismic prone regions, one of the most interesting applications of Structural Health Monitoring (SHM) is the management of the emergency induced by earthquakes on railway infrastructures. This involves decisions about possible restrictions aimed to keep an appropriate level of safety while minimizing costs. Restriction decisions may include the continuation, limitation or halting of traffic and structural operations. This study proposes an ad-hoc methodology of loss-driven warning protocol for a viaduct of the Campania region of Italy. This viaduct connects the Quarto-Centro and Quarto stations of the line Circumflegrea. The decisional procedure several approaches associated with accelerations and displacements of the bridge. This methodology provides immediate actions to undertake either operational or severe conditions consequent to an earthquake. Hence, it presents a modern and efficient response under critical states of the viaduct.