NORMA: a tool for the analysis of Relay-based Railway Interlocking Systems

Abstract

We present Norma, a tool for the modeling and analysis of Relay-based Railways Interlocking Systems (RRIS). Norma is the result of a research project funded by the Italian Railway Network, to support the reverse engineering and migration to computer-based technology of legacy RRIS. The frontend fully supports the graphical modeling of Italian RRIS, with a palette of over two hundred basic components, stubs to abstract RRIS subcircuits, and requirements in terms of formal properties. The internal component based representation is translated into highly optimized Timed nuXmv models, and supports various syntactic and semantic checks based on formal verification, simulation and test case generation. Norma is experimentally evaluated, demonstrating the practical support for the modelers, and the effectiveness of the underlying optimizations.

Applicability of Magnetic Sensors in Interlocking Systems

“…The increased reliability of relay interlockings serves as a deterrence for many network managers to upgrade to the latest technology, especially on branches where the rail traffic is not intensive. From a design point of view, relay interlockings are the standard against which modern electronic interlocking systems are compared to when evaluating their performances [10].…”

“…A unique challenge posed by the persistence of these legacy systems is that fewer railway specialists possess a deep and comprehensive understanding of them [10]. This unmet need of qualified personnel may lead to increased waiting times when dealing with disruptions of the interlocking.…”

“…Such simulations are dependent on reliable and accurate interlocking models. The generation of these models usually involves the digitalization of existing relay schematics either in a specially designed schematics software [10] or by recoding them as an XML file [11]. The language used to describe the behavior of relay interlockings is usually Boolean [12] or LLD [13].…”