A Transit Agency Guide to Evaluating Secondary Train Detection/Protection Systems in Communications-Based Train Control (CBTC) Systems

According to the 1474.1-2004-IEEE Standard for Communications-Based Train Control (CBTC) Performance and Functional Requirements: “A CBTC system is a continuous, automatic train control system utilizing high-resolution train location determination, independent of track circuits; continuous, high capacity, bidirectional train-to-wayside data communications; and train-borne and wayside processors capable of implementing automatic train protection (ATP) functions, as well as optional automatic train operation (ATO) functions, and automatic train supervision (ATS) functions.” CBTC control philosophies can allow trains to operate safely at shorter headways and permit system operations to recover more rapidly in the event of service delays; all of which can offer a more regular and improved passenger service which can translate into increased line capacity constrained only by the performance of the rolling stock and the limitations of the physical track alignment. One of the fundamental operational benefits of CBTC systems is that movement authority limits are no longer constrained by physical fixed-block boundaries but are established through train position reports that can provide for “virtual block” or “moving block” control philosophies. According to FTA Report 45, An Assessment of the Business Case for Communications-Based Train Control: “To date, deployment of CBTC technology within the United States has been limited, due, at least in part, to a perception of higher costs associated with the implementation of this technology. This perception of higher costs is in turn driven, in part, by a perception that CBTC systems require a secondary track circuit-based or axle counter-based “fall-back” system to detect and protect trains in the event of CBTC system failures.” Research is needed to provide guidance to transit agencies considering CBTC, particularly as it relates to secondary train detection/protection systems. The objective of this research is to develop guidelines to enable a transit agency to evaluate the need for (1) secondary train detection/protection systems or (2) operating practices in lieu of detection/protection systems when implementing a CBTC system. The research is complete and published as TCRP Web-Only Document 71: A Transit Agency Guide to Evaluating Secondary Train Detection/Protection Systems in Communications-Based Train Control Systems. The WOD provides a practical approach to evaluating the appropriate level of secondary train detection/protection systems (STD/PS) for a given communications-based train control system application. In terms of detection, track circuits and axle counters are both considered and compared, including the broken rail detection capabilities of track circuits and the possibility of having no secondary detection at all.


  • English


  • Status: Completed
  • Funding: $197624
  • Contract Numbers:

    Project D-18

  • Sponsor Organizations:

    Transit Cooperative Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC    20001

    Federal Transit Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Performing Organizations:

    CH2M Hill

  • Principal Investigators:

    Diemunsch, Kenneth

  • Start Date: 20160205
  • Expected Completion Date: 20170703
  • Actual Completion Date: 20170703

Subject/Index Terms

Filing Info

  • Accession Number: 01712953
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project D-18
  • Files: TRB, RiP
  • Created Date: Jul 29 2019 3:26PM