Customer satisfaction is essential for public and railway services, because firms in these industries have contracts with governments requiring them to achieve specific customer satisfaction targets. In this paper, we describe a National Dutch Railways project in which we identify the major determinants of customer satisfaction. By combining multiple data sources, we link operational and marketing data to customer satisfaction. Our models show that train punctuality and sufficient seating within a train are important factors in customer satisfaction, as are other service elements, such as the availability of Wi-Fi in a train and the condition of facilities at a station. Drawing on the model results, the National Dutch Railways pursued initiatives to increase customer satisfaction. Among these initiatives is the development of an application that allows passengers to check seating availability, the design of a marketing dashboard reflecting developments in customer satisfaction, and the creation of a tool to identify the most critical determinants of customer satisfaction.