Evolution of Communication Based Train Control worldwide

The paper summarises the evolution of rail signalling system from track-circuit signalling to advanced Communication-Based Train Control (CBTC) systems, highlighting the differences, benefits and challenges with regard to improving performance while ensuring safety. It describes the evolution of such systems over the last three decades; from wayside signals to cab signals, to profile-based systems, to communications-based train control systems for an effective means of overcoming the fundamental limitations of the conventional track-circuit based system. CBTC allows trains to operate with much closer headways while ensuring safe train separation and better train control flexibility. Not only do CBTC systems determine the position of the train with a higher degree of accuracy independently of the track circuits, but also offer bidirectional train/wayside communication to enhance train operations and supervision. Operational and performance benefits realised with the newer technology systems are discussed, together with the challenges of implementing such systems. Standardisation for Communication Based Signalling System initiatives is also described and industry trends presented.