An interlocking system monitors the status of the objects in a railway yard, allowing or denying the movement of trains, in accordance with safety rules. The high number of complex interlocking rules that guarantee the safe movements of independent trains in a large station makes the verification of such systems a complex task, which needs to be addressed in conformance with EN50128 safety guidelines.#R##N##R##N#In this paper we show how the problem has been addressed by a manufacturer at the final validation stage of production interlocking systems, by means of a model extraction procedure that creates a model of the internal behaviour, to be exercised with the planned test suites, in order to reduce the high costs of direct validation of the target system.#R##N##R##N#The same extracted model is then subject to formal verification experiments, employing an iterative verification process implementing slicing and CEGAR-like techniques, defined to address the typical complexity of this application domain.
['Andrea Bonacchi', 'Alessandro Fantechi', 'Stefano Bacherini', 'Matteo Tempestini']
Validation process for railway interlocking systems