Statechart has been utilized as a visual formalism for the modeling of complex systems. It illuminates the features on describing properties of causality, concurrency and synchronization. The reachability structure is used to represented dynamic model by a Boolean function. In this paper, we try to describe State invariant method and equation function for hierarchical tree diagram. Finally, we used them to analyze the urban traffic control systems which are modeled by using Statecharts. Their formalism provides a concept of propositional logic for presenting control strategy.