Technical Reports

Safety of Vital Control and Communication Systems in Guided Ground Transportation. Analysis of Railroad Signaling System: Microprocessor Interlocking

  • 01
  • May
  • 1993
AUTHOR: Simon Reich, Thomas Bessoir
OFFICE: RPD
SUBOFFICE: RPD-30
REPORT NUMBER: DOT/FRA/ORD-93/08
KEYWORDS: Microprocessor-based systems; interlocking system; central processing unit; integrated circuits
ABSTRACT: The study has been conducted with the goal of gaining an insight into the issues of maintaining vital signal systems implemented with microprocessor chips and of making field changes to the application of such systems. To relate these abstract topics to concrete issues, two actual commercial systems were investigated, namely the General Railway Signal Company VPI Vital Processor Interlocking and the GRS GENRAKODE microprocessor-based coded track circuit system. One of the purposes of the study is to determine what actions should be taken by railroads to maintain signal-system safety when microprocessor-based signal systems receive maintenance to correct a failure and when such signal systems are modified after installation because of application changes such as a revision to the track plan or the signal aspects. A second purpose of the study is to determine whether revisions are required to the Rules, Standards and Instructions Governing the Installation, Inspection, Maintenance and Repair of Signal and Train Control Systems, Devices, and Appliances (RS&I) due to the introduction of microprocessor-based signal systems and to suggest such revisions if they are indicated. These revisions, if any, would be based on the recommendations for maintenance and field-change procedures identified in the first part of the study.

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