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.

Site Notification

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

Broken Rail and Rollout Detection to Support QMB Operations

Document Series
Technical Reports
Federal Railroad Administration
Report Number
Subject Positive Train Control
Positive Train Control, PTC, Quasi-Moving Block, QMB, next generation track circuit, NGTC, track circuit enhancements

Researchers collaborated with a railroad advisory group to demonstrate the validity of a track circuit concept that supports the Quasi-Moving Block (QMB) method of train control. They performed proof-of-concept testing, capacity analysis, hazard analysis, and requirements development. 

QMB is one of three new additional modes of train control that have been identified as an evolution of today’s Positive Train Control (PTC); namely, Enhanced Overlay PTC (EO-PTC), QMB, and Full Moving Block (FMB). QMB inherits the capacity benefits of EO-PTC and provides additional safety benefits compared to PTC. However, QMB remains limited by the fixed track circuit blocks and does not provide significant capacity benefits beyond EO-PTC unless supplemented by potential modifications to track circuits that, together with QMB and vital rear-of-train location, provide further capacity benefits.

Last updated: Tuesday, July 12, 2022