USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Full Moving Block (FMB) Concept and Requirements Specification for Railroad Operations

Document Series
Research Results
Federal Railroad Administration
Report Number
RR 23-23
Subject Communications, Train Control
Alternative Broken Rail and Rollout Detection (ABRRD), Full-moving block (FMB), Quasi-moving block (QMB), Interoperable Train Control (ITC), Positive Train Control (PTC), communications-based train control (CBTC)

The Federal Railroad Administration sponsored Transportation Technology Center, Inc., (MxV Rail), in collaboration with a rail industry stakeholder technical advisory group (TAG), to refine concepts and develop interoperable requirements for the Full Moving Block (FMB) method of train control. The team worked to develop an FMB Concept of Operations (ConOps) document with a focus on interfacing with alternative broken rail and rollout detection (ABRRD) system architectures; develop an Incremental FMB System and Segment Requirements Specification document; develop ABRRD system requirements; redline the Interoperable Train Control (ITC) Office-Locomotive Segment Interface Control Document (ICD), as well as the ITC Wayside-Locomotive Segment ICD, to capture recommended changes; develop migration considerations; and conduct a preliminary safety analysis. Research was conducted from May 2020 to September 2022.

DOT is committed to ensuring that information is available in appropriate alternative formats to meet the requirements of persons who have a disability. If you require an alternative version of files provided on this page, please contact
Last updated: Wednesday, November 29, 2023