Structural health monitoring is applied increasingly to supervise and evaluate existing or new structures. The measured values are used for example to verify the computational assumptions, or for assessing the long-term behavior. In contrast, a different field of application is the safety monitoring of critical construction phases using a monitoring system, which is equipped with automated warning and alarm messages. Such a system was used during the construction of deep foundations and embankments of railway bridges over the river Aller and the creek Wätern. The aim of the system was to timely detect critical changes under railway and construction loads. The monitoring system was planned as a compensatory measure for the reduced level of safety during the replacement of the damaged bridges. Within the interaction between bridge owner, construction supervisor and monitoring expert, the monitoring has proven to be a powerful tool to ensure a safe railway operation even under structural works.