**4. Conclusions**

The methodology of Standard Elements is suitable for all infrastructure assets. Deriving deterministic maintenance cycles is only possible for assets with a weardriven and thus loading-driven behavior (track, switches, bridges, catenary), in case of stochastic failure-driven assets (signaling) the working cycles depict probabilistic maintenance frequencies.

The Standard Element Approach is implemented at several railway infrastructure companies. Austrian Federal Railways, Swiss Railways [28], Scandinavian infrastructure companies, and railway companies in the Balkans, and in the Caucasus area. It always is the first step for implementing sustainable track asset management. In the past, the methodology led to new regulations for track components, specified for the different sets of parameters and thus a specific use (e.g., rail steel grades).

While the first implementations were primarily based on experience, progressive digitization, and more data in longer time series, allow for further specification and detailing of the Standard Elements. Working cycles can nowadays increasingly be based on deterioration functions derived from trend analyses of time-sequenced data. It should be noted that the basic thrust has not been lost by further detailing and that fine-tuning based on prognoses of track behavior is already taking place.

Essential specifications and extensions of the methodology are currently on the way. Thanks to new data, it is now possible to consider also the track work quality. In addition, more specific transport data is available allowing for considering wheel-rail interaction and also optimization within the parameter transport volume [23]. In addition, the model is currently being expanded to include environmental aspects.

CO2 equivalents are calculated for track components, track work, and the end-of-life scenario and considered in the economic evaluation [29–31].

All these developments are possible due to additional and more specific data enabling more detailed working cycles. An adaption of the principles of the methodology of Standard Elements itself is not necessary.
