Supervisory control of roadside units

A third of the Dutch highways is monitored and controlled by roadside units. These RSUs are safety-critical systems, as they safeguard roadworks and accidents. Therefore, it is essential to have guarantees on the correctness of the roadside unit controller. Using supervisory control theory, a correct-by-construction supervisor is obtained from a model of the system and its requirements. From the supervisor model, a controller implementation can be obtained automatically. There are many roadside units sharing the same basic components, but in different numbers and configurations. To take advantage of this, parametric models are used. Subsequently, these models can be used to create different models for different configurations of an roadside unit. The purpose of this paper is to show the applicability of supervisory control theory to roadside units. To this end, parametrized models of the components of an roadside unit are presented. The models are used to synthesize a supervisor for a specific roadside unit, which is validated using simulation. After validation, a controller implementation is generated from the supervisor model. The implementation is then validated using hardware-in-the-loop simulation.