On the real time modeling of interlocking system of passenger lines of Rawalpindi Cantt train station

Abstract

Purpose: Recent advancements in technology have enabled railway organizations to shift from manual to computer based automated interlocking systems for increasing their efficiency and profits. Since automated systems are complex and interlocking systems are safety critical systems, these systems should be modeled and verified against safety requirements to weed out any design bugs which might lead to catastrophes during their system life cycles. In this study, we model software based automated interlocking control system of a train station, located at Rawalpindi Cantt (Pakistan). Methods:We have modeled software based automated interlocking control system using timed automata and verified its correctness using UPPAAL model checking software. Timed automata have successfully been used for the modeling and verification of real-time systems.Results: We constructed a real-time model of railyard interlocking system by employing a model-checking approach to determine behavior of the model under various conditions. The model checker ascertains the absence of errors in a system by inspecting all the possible states or scenarios of the modeled system. The results show that important properties related to the safety of the designed interlocking system of the railyard management system can be verified using our presented approach. These properties ranged from collision and de-railment avoidance to checking the correct error handling functionality of the timed automata models. Conclusions: The final modular design can easily adapt to the route upgrades and changes within the station by simple variable adjustments. Based on the laid down methodology and verification techniques, this study can be further built upon, extended and linked to cover the shunting aspect of the train station operations, run through operations, introducing automatic train stop (ATS) functionality and recommend three to four aspect traffic signaling for the train station. This study takes a first step in providing an indigenous solution to an indigenous problem of designing an upgraded and verified signaling infrastructure for Pakistan Railway's Rawalpindi Cantt train station.

Formal Modeling and Data Validation of General Railway Interlocking System

“…For example, Literature [8] proposed the MPN (Mobile Petri Net) approach based on the Mobile intelligent agent and Petri Net, which was used to model the interlocking system and verify it by reachability graph. Literature [9] established the time automata model of interlocking system using UPPAAL software and verified the safety related properties. In the literature [10] the model of interlocking system which accommodated the sequence release was built, using a combination of SMT (Satisfiability Modulo theory) based Bounded Model Check and inductive reasoning, the safety properties were verify.…”

A New Algebraic Approach to Decision Making in a Railway Interlocking System Based on Preprocess

“…Remarks. The approach presented in this paper only focuses on the safeness of the proposed situation; meanwhile other approaches like [23,34] also consider other properties such as reachability of sections or the situation of the switches of the turnouts under a train (that shouldn't be changed under any circumstance to avoid derailments due to a premature change of the switch during the transit of the train). Another issue not treated in our model is the confirmation that the switches of the turnouts and the light signals have really been set to the ordered situation (something considered, for instance, in [34]; this latter approach uses a real-time system, a flexible approach with a wide variety of applications [21]).…”

“…On the other hand, our new approach can handle really big layouts (like the one in the example of Table 1, with, as said above, 300 sections and more than 200 turnouts and light signals, what is a far bigger layout than any one that we have found treated in real time). For instance, the authors of [34] mention that "our study is unique in the fact that modeling and verification of mid to large size railway yard is being undertaken in UPPAAL model checker (. .…”

Abstract State Machines and System Theoretic Process Analysis for Safety-Critical Systems

“…That paper shows that the SOFL provides an effective means to allow the developer to take a gradual process to build a formal specification for the system, but it does not show how to verify or validate the resulted specifications. In [16], timed automata is chosen to model the railyard interlocking system, and UPPAAL model checker is used to verify the safety properties of that system. On one hand, UPPAAL, unlike ASM, lacks structuring mechanism to achieve abstraction [20], and on the other hand, UPPAAL does not fully support CTL model checking [10].…”