A Practical Risk Assessment Methodology for Safety-Critical Train Control Systems
REPORT NUMBER: DOT/FRA/ORD-09/15
KEYWORDS: Accident reduction, risk assessment, Base Case risk, Proposed Case risk, acceptable safety 12performance limit, tolerable hazard rates
ABSTRACT: This project proposes a Practical Risk Assessment Methodology (PRAM) for analyzing railroad accident data and assessing the risk and benefit of safety-critical train control systems. This report documents in simple steps the algorithms and data inputs that are required to calculate the collective risks associated with a proposed system (such as a positive train control system). These risks are in turn compared with a reference safety target (such as the risk associated with the existing system or method of operation that the proposed system is intended to replace) to arrive at the quantitative hazard rates that proposed system must be designed not to exceed. These hazard rates, called tolerable hazard rates, form a key part of the safety requirements specification for the proposed system. A software tool has been developed for use by risk analysts safety engineers to implement the steps of PRAM in an iterative manner.
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