Moving block railway signalling

An examination is made of the performance of four and five aspect fixed block signalling, theoretical pure moving block signalling, and a more practical quantised moving block system, when operating under both steady state and perturbed running conditions. For each signalling system, a number of basic geographical components, which are commonly found in a railway network, are analysed in order to determine their maximum capacity for a wide range of steady state operating conditions. An example is included of an algorithm which may be used to combine a number of these basic components to facilitate analysis of a more complex configuration. In the investigation of perturbed operating conditions, a specific delay is imposed on a train, and, with a range of running headways, the resulting delays to subsequent trains are evaluated for each signalling system. Thus, it is possible to decide if a signalling system is stable under a given set of operating conditions. Also, if the system is stable, the total number of trains which experience some delay may be determined. Finally, an examination is made of a line which simultaneously carries high speed trains, operating under moving block, and low speed trains, operating under fixed block signalling.