Implementation of the European Train Control System (ETCS) Level 2 requires that a huge amount of physical balises (known as Eurobalises), used to determine each train’s position and direction of motion, be deployed in order to support safe operation of high-speed/high-frequency train services all along the European railway infrastructure. The associated costs are substantial, which motivates the investigation of cheaper technologies. One important candidate technology is GNSS positioning, which in principle would considerably reduce the number of required Eurobalises, many of them being replaced in favour of so-called Virtual Balises. A virtual balise implies the installation of no physical devices on the trackside. Hence, the more physical balises can be replaced by virtual ones, the larger the cost reduction.