SysML has several modeling techniques for defining the behavior of a system. In this talk, we have a closer look on modeling system behavior using activity diagrams and the underlying semantics of these diagrams.  Next, we take a dive into the usage of SysML Activity Diagrams within the generic tunnel control system models of Rijkswaterstaat. Inspired by this usage, restrictions on the modeling language and its elements are defined which allow for an optimized translation to formal models.