Automatic Evaluation Framework for Reliability and Safety of Multiple Train Detection Systems

Abstract

A train detection system is the basis of signaling and control in railway transportation, and there is a trend to apply multiple train detection systems simultaneously to improve reliability and safety. The ideal evaluation process for train detection systems should be able to determine their reliability and safety by considering the track layout, detection block, design and logic of the detection system, routing and frequency of trains, and train length (in relation to block length). Existing evaluation methods for train detection systems still require a few manual interactions and human judgment, which could be inefficient and subjective. Consequently, this research aims to develop a framework with automatic processes to generate all failure scenarios, calculate the probability of fail-safe conditions and wrong-side failures, and finally determine the reliability and safety index of the corresponding connection logic. Results of case studies demonstrate the applicability of the proposed framework to actual cases. The use of this framework can assist railways in identifying the appropriate design and logic of multiple train detection systems.

Xác định các chỉ số đánh giá an toàn hệ thống tín hiệu điều khiển chạy tàu hiện đại

“…Ngoài các khái niệm sự kiện bất ổn định nguy hiểm còn có khái niệm sự kiện bất ổn định không nguy hiểm. Chúng là nguyên nhân chuyển chuyển động của đoàn tàu sang trạng thái không đủ tiêu chuẩn chạy tàu nhưng không nguy hiểm, nó làm giảm hiệu quả của quá trình vận chuyển nhưng không ảnh hưởng tới mức độ an toàn [10]. Ví dụ là trở ngại nào đó dẫn tới động cơ sức kéo của đầu máy giảm sức kéo, nó sẽ dẫn đến làm giảm tốc độ của đoàn tàu là trở ngại không nguy hiểm.…”

Template-Based Voting Logic for Dual Train Detection Systems

“…Considering that all the blocks are equipped with two detection systems, if inconsistent outputs are obtained from dual detection systems, which output must be chosen for the block is a matter for some debate (21). Thus, the TRA has used three design logics to handle this situation, namely, serial connection (2 out of 2), parallel connection (1 out of 2), and primary-secondary connection.…”

“…As shown in Table 1, the serial connection in dual train detection systems should be designed so that ''only when both two systems show cleared would the whole system show cleared.'' Based on previous research (21), this logic would increase safety, given that if any of the systems detected the train, the entire system would detect the train. However, it would suffer from low reliability.…”

“…The second module calculates the probability of each scenario, categorizes the scenarios by failure type, and finally obtains the reliability and safety index for a particular design logic; this represents the improvement ratio over the base case and can be viewed as the reliability and safety performance for this logic. In the formulas of the two indices in Figure 1, Prob s indicates the probability of scenario s, REL l indicates the scenarios that are related to the performance of reliability in logic l, WSF l indicates that a wrong-side failure exists in the logic l scenario, and l = b represents the base case (21). To render the indices more intuitive, we subtract the ratio from 1.…”

“…Given the performance deficiency of the track circuit, the conventional railway operator in Taiwan, TRA, has been replacing track circuits with two-axle counter systems since 2012. However, doubling the number of detection systems per block has not substantially improved the system reliability (21), and also poses safety risks in train operations, such as the Jiadong Station incident. Overall, existing design logic for dual detection systems cannot fully and simultaneously improve track system reliability and safety.…”