Validation process for railway interlocking systems

Abstract

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.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. 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.

Efficient verification of railway infrastructure designs against standard regulations

“…All technical rules presented herein are based on the Norwegian infrastructure manager's regulations. 4 The goal of the consistency checking is to confirm that no inconsistencies exist, in which case no further information is required, or to find inconsistencies and present them in a way that allows the user to understand the error and to adjust their design accordingly. Rules are therefore expressed negatively, as rule violations, so that a query corresponding to the rule is empty whenever the rule is consistent with the design, or the query contains counterexamples to the rule when they exist.…”

“…This suggests that the details of object placement at one station seldom influence the object placements at another station. Such locality of properties has been earlier exploited by other railway verification approaches, e.g., [23] or [4]. Bonacchi et al [4], in particular use locality to split model checking problems into smaller pieces, and using topology data to optimize variable ordering in BDD-based verification.…”

“…Such locality of properties has been earlier exploited by other railway verification approaches, e.g., [23] or [4]. Bonacchi et al [4], in particular use locality to split model checking problems into smaller pieces, and using topology data to optimize variable ordering in BDD-based verification. For incremental Datalog verification, locality of rules would mean that predicates which depend on graph connectedness would have a bound on the search depth needed to update results after a single object's change.…”

Compositional Verification of Interlocking Systems for Large Stations

“…This principle has been exploited in [22] to define domain-oriented optimisation of the variable ordering in a BDD-based verification. Locality can be used also for slicing, as suggested in [3,9,8,1]: the idea is to consider only the portion of the model that has influence on the property to be verified, by a topological selection of interested track elements (therefore closely related to the cone of influence of the property): this allows for a much more efficient verification of the single property, but comes at the price of repeating the slicing and the verification for every property, and of separately checking that verifying slices does actually imply the satisfaction of desired properties for the whole system. Nevertheless, it appears that when automated, this process can offer significant time and memory savings.…”

Integration Research of Communication Based Train Control and Computer Interlocking in Urban Rail Transit

“…In order to verify the feasibility of the integrated system scheme, referencing the verification method of train control system and interlocking system [9][10][11], on the simulation platform of the rail traffic signal system with the existing interlocking system, the software has been used to simulate the control function of the area integrated controller, and the concrete control process is carried out as shown in Figure 3. The experimental interface is developed by VC++6.0 program, as shown in Figure 4, and urban rail transit main track signal layout is selected as the reference computer simulation design.…”