T   T: a S  R O P

Railway optimization problems have been studied from a mathematical programming perspective for decades. This approach is particularly well suited to model the multitude of constraints that typically arises in the context of a railway system. In recent years, these problems have attracted some attention in the algorithms community, with a focus on individual problem aspects, in an attempt to understand precisely where the inherent complexity of railway optimization lies. We sketch the state of affairs by discussing a few selected examples at different levels of detail.