Post-Incident Safety Analysis of an Automatic Train Protection System

Abstract

Rail is used as a form of transportation by millions of people each day. Many of these rail transit systems utilize 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 discusses the results of a post-incident safety analysis performed on an ATP system. A Fault Tree Analysis (FTA) was performed on a vehicle ATP subsystem following several incidents involving a compromise in system safety. The results of the FTA showed that the vehicle ATP subsystem did not meet the “fail safe” design criteria. This paper uses the results of the FTA to identify possible safety improvements.