srosatsfne, that is actually not a brake, since you can notice that there is never any contact with the wheels. I have stood there watching the train pass through this, and it seems just to a sensor that could monitor the speed of the train for the station. They might use it to give them a time frame for dispatch of the train in the station.
-----------------
The world's a roller coaster and I am not strapped in, maybe I should hold with care, But My hands are busy in the air- Incubus