ERTMS reduces the possibility for human error providing a comprehensive automatic train protection (ATP) function, where this does not yet exist. ERTMS works as a safe monitoring system, continuously supervising the speed of each train according to track and train data. If the actual train speed exceeds the permitted data, brakes are applied automatically. This ensures the train will be stopped in front of the danger point. This, coupled with the flexibility of ERTMS which can be applied to low-density as well as to high-density lines, is particularly important for countries where ATP systems are not yet widely deployed.