Lessons Learned from a System Safety Analysis of an Automatic Train Protection System

摘要

Rail is used as a form of transportation by millions of people each day. Many of these rail transit systems utilize, to some extent, automatic operation. Automatic operation of rail transit vehicles is provided by an Automatic Train Control (ATC) system, which is typically partitioned into three subsystems: Automatic Train Protection (ATP), Automatic Train Operation (ATO), and Automatic Train Supervision (ATS). This paper will show how a system safety analysis can be used to identify weaknesses in ATP systems and how the safety of automatic operations can be improved. A Fault Tree Analysis (FTA) was performed on an ATP system to identify weaknesses in a train's safety system. The results of the FTA showed that the Carborne portion of the ATP system did not meet the "fail safe" design criteria. This paper uses the results of the FTA to identify possible safety improvements. The safety of the Carborne ATP subsystem was then reevaluated incorporating the identified improvements to show the attainable increase in safety.