One of the most responsible and most challenging construction tasks are tunnel excavation and stabilization. Tunnel excavation and support system were developed back in the nineteenth century and significant advances in technology were achieved in the second half of the twentieth century. In order to reduce the risk safety management systems were established. Such system also includes the monitoring, apart from the design requirements on excavation and support and the assessment of stability during construction. Monitoring has the purpose frequently observation and adjustment of excavation and support system to actual soil conditions. Unfortunately, all measures of monitoring are defined only for the tunnel construction period. In Croatia, there are no technical standards for tunnel monitoring during the exploatation. The aim of this paper is to point out the importance of methodology and monitoring procedures that would detect changes in time and ensure the tunnel sustainability. Tunnel monitoring implies a set of operations that can promptly register the events and conditions that could affect the stability, traffic safety and tunnel durability

: tunnel, monitoring, tunnel sustainability, traffic safety