The paper defines Automatic Train Protection (ATP) and Cab Signalling. It reviews the recent history of development of both, and describes the effects of both continuous and intermittent systems on capacity. The risks of installation and maintenance of lineside-orientated systems are highlighted, along with the benefits of removing the infrastructure to track-remote locations. Finally, the emergence of the European Train Control System (ETCS) is explained, together with the many advantages it offers.
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