Formal modeling and analysis of railway operations with active objects

We present a comprehensive model of railway operations written in the active object language ABS. The model is based on specifications taken from the rulebooks of Deutsche Bahn AG. It is statically analyzable and executable, hence allows to use static and dynamic analysis within one and the same formalism. We are able to combine aspects of micro- and macroscopic modeling and provide a way to inspect changes in the rulebooks. We illustrate the static analysis capability by a safety analysis based on invariant reasoning that only relies on assumptions about the underlying railway infrastructure instead of explicitly exploring the state space. A concrete infrastructure layout and train schedule can be used as input to the model to examine dynamic properties such as delays. We illustrate the capability for dynamic analysis by demonstrating the effect that different ways of dealing with faulty signals have on delays and propagation of delays.