The objectives of Asset Management transport infrastructure are to ensure secure (reliable and safe) service of the individual objects and/or network, to preserve the infrastructure capital and to maintain infrastructure function through their life-cycle.

Maintenance activities should preserve or modify the performance and future serviceability of a structure in such way that an adequate level of reliability with respect to performance requirements applicable to the structure under consideration is preserved or achieves. Hence adequate maintenance should guarantee reliability, safety functionality, availability, maintainability, health and security, as well as environmental and economic performance at the politically agreed level of service, anticipated by the designer and corresponding with the stakeholders needs.

In order to arrange maintenance resources, the concept of condition-states and minimum maintenance thresholds are widely used in context of maintenance planning in many European countries for the maintenance of bridges and infrastructure systems. However, there is no uniform approach to defining and rating the condition-states and setting the low limit maintenance thresholds. In general, national authorities or individual operators are using their own developments which consequently lead to different levels of service with regard to e.g. safety, reliability and availability.

In many cases, the models and criteria used are based on the country-specific experience with implementation of condition-based maintenance strategies. Moreover, in some European countries preventive maintenance uses both condition-based and scheduled maintenance strategy, with certain maintenance measures (e.g. rehabilitation) carried out in a condition-based manner and some other measures (e.g. cleaning, deforestation) are planned/fixed at certain intervals. Nevertheless, the minimum condition requirements associated with maintenance thresholds are frequently not clear or are variable over time.

In this contribution based on the outcomes of H2020 IM-SAFE project, maintenance concepts, condition-state definitions and low limit thresholds of maintenance strategies of European countries will be presented, discussed and compared.