The U.S. National Renewable Energy Laboratory (NREL) has developed a range of open-source tools to enhance understanding and advancement in transportation and mobility technologies. These tools help stakeholders optimize efficiency, reduce emissions, and promote the clean energy transition. NREL's modeling tools, such as ALTRIOS for railways and FASTSim for vehicle technology, aid in decarbonization efforts by simulating technology impacts. The Highly Integrated Vehicle Ecosystem Simulation Framework (HIVE) allows for the analysis of electric vehicle fleet operations and energy efficiency in mobility services. Additionally, NREL's Open Platform for Agile Trip Heuristics (OpenPATH) enables individuals to track their energy consumption and carbon footprint based on travel mode. These tools provide valuable insights for decision-makers, communities, and individuals looking to make more sustainable transportation choices.