In this thesis I describe the modeling and implementation of a simulation tool (AGSIM) used to study an Automated Guided Vehicle (AGV) based car body manufacturing system. The tool implements a control strategy which deals with breakdown situations and examines this strategy in terms of flexibility and agility. The system is modeled with two approaches to better understand the dynamic nature of the system. An object oriented model of the system is created based on Rumbaugh's Object Modeling Technique (OMT) and the system is modeled using Petri nets with extensions. The modeling approaches are compared. The AGSIM tool is implemented in C++ and uses Tcl/Tk for the graphical user interface. The tool allows a user to create, edit, save, and restore manufacturing layouts, object parameters, and simulation state. The system validates the layout and initial automated guided vehicle marking, it dynamically creates the necessary objects, and it graphically displays the simulation progress. The user can simulate the effect of a breakdown and view the results of one breakdown control strategy.