the transparent data balises are connected to the older distant and stop signals. Given the lower maximum speed of the rapid transit system the Eurobalises can be placed at shorter distance (every four sleepers). The cab computer software is much simpler as the weight of the train can be inferred from an assumed maximum. The sum of advantages makes the system faster and cheaper than using a plain ETCS level 1 train protection system. References Notes: External links video presentation on ZBS, Tobias Grimmel, Technische Universität Berlin, 3. December 2009 Train protection systems Railway signalling in Germany