This report summarizes a series of three workshops on rail decarbonization hosted by the Federal Railroad Administration (FRA). These internationally attended workshops laid the foundation for future decarbonization research topics, funded through FRA’s Research, Development, and Technology (RD&T) Program’s Broad Agency Announcement (BAA). The BAA’s Energy and Emissions topic statement within the Rail Energy, Emissions and Engine (Rail E3) Technology Research Program is a direct result of the first two workshops. This program prioritizes research into the safety and efficacy of emissions reduction and energy efficiency improving technologies. FRA-sponsored decarbonization research projects supported the development of standards for alternative fuel locomotive fuel tenders, development of a dual fuel hydrogen internal combustion engine, testing of blends of biodiesel and diesel fuel in a Tier 4 single cylinder test engine, development of the Locomotive Waste Heat Recovery System, and reduction of Greenhouse Gas emissions, Regulated Emissions and Energy Use in Technologies (GREET) model. Achieving the Administration’s goal of attaining Net-zero emissions by 2050 requires rail industry-wide collaboration in R&D and implementation of technologies. Therefore, FRA intends to continue its collaborative research efforts to these ends.