Describes the context for and creation of a strategic planning model of a major US railway. The key factors in choosing a system dynamics approach are presented, and the synergy between the new model and the existing suite of planning applications is highlighted. The overall structure of the model is reviewed, including the key reinforcing and balancing loops, and model creation issues, such as level of aggregation, are discussed. The methodology followed in the data collection and calibration phases is described in detail, and samples of calibration metrics and sensitivity testing parameters are provided, as well as sample model output. Lastly, potential future uses of the model are noted.