Abstract

Brake is a safety critical system for railway vehicles and brake failures have caused many catastrophic accidents in the history. Detailed accident investigation reports are available and National Transportation Safety Board (NTSB) also makes safety recommendations to Federal Railroad Administration and the industry. However, there is limited research on how to improve the brake safety from the perspective of design, system integration and safety analysis. In this paper, a framework for braking safety design and analysis is introduced, which includes four parts: failure alarming system, safety design, safety analysis and preventative maintenance. For failure alarming, according to the severity level, the failures will be notified to the operator, to Operation Control Center (OCC) or saved for the maintainer. For safety design, redundant design for fail-safe feature, automatic braking, brake release, weight control, ergonomics design for easy operation and maintenance are discussed and several application examples are illustrated. In the safety analysis section, Preliminary Hazard Analysis (PHA) as a semi-quantitative analysis, Failure Modes, Effects, and Criticality Analysis (FMECA) as a bottom-up method and Fault Tree Analysis as a top-down method are used. The hazards details, system assurance actions and closure references are recorded in the Hazard Tracking Log (HTL) to ensure all the safety related items are well tracked and documented. Preventative Maintenance (PM) which is regularly performed on the brake components to lessen the likelihood of failing is also discussed in combination with the reliability prediction and safety analysis for a balance of safety and economy. The safety design framework and principles introduced in this paper can also be applied into other railway systems, such as Propulsion, Signaling, Doors, etc. and may provide insights to similar industries such as automotive, energy and so on.

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