The article discusses the importance of freight rail in the United States economy and its relatively low environmental impact compared to other transportation modes. Major railroads are exploring sustainable practices and researching alternative fuel technologies like battery-electric locomotives. The introduction of energy storage tender cars, which act as onboard energy storage systems, is seen as a solution to the range limitations of battery-electric propulsion systems. Various global research initiatives and test operations are mentioned, emphasizing the growing interest in sustainable energy solutions for freight trains. The development of a convex optimization model to determine the optimal number of energy storage tender cars based on market characteristics, costs, and technology parameters is highlighted. This model aims to balance payload, range, and costs efficiently for different freight markets. The article provides numerical examples and demonstrations of the model's application in real-world scenarios, showcasing its potential for enhancing the sustainability of freight transportation. Overall, the sentiment of the article is positive, focusing on the advancements in alternative fuels and the potential for optimizing energy storage tender cars to achieve sustainable freight operations.