In a research project funded by FRA from May 2020 to September 2022, Transportation Technology Center, Inc. collaborated with a railroad industry technical advisory group to develop 1) the concept, 2) the system-level, segment-level, and interface requirements, 3) the migration considerations, and 4) the initial safety analysis for an Interoperable Full Moving Block (FMB) method of train control. The fundamental objective of FMB is to achieve safety and near theoretical maximum capacity benefits without the artificial constraints inherent in fixed block operations. Through research efforts and guidance from the TAG, the team concluded that the O-PTC and QMB architectural foundations can be fully leveraged for the implementation of FMB with minimal incremental changes.