Transactions on the Built Environment vol 34, © 1998 WIT Press, www.witpress.com, ISSN 1743-3509 State of the art of computer application to the railway traffic control and automation Giuseppe Sciutto* & Giacomo Astengo^ * University ofGenova via all Opera Pia 11 a, 16100 Genova, Italy 7e/. J9 70 JJJ2747 Fox. JP 70 JJJ2700 * Sciro Electra S.r.l. Via Fieschi, 25/6a 16121 Genova, Italy 7W J9 70 J7026J2 Fm:. J9 70 J70270J Abstract The Computer-based technologies are presently largely applied to the railway traffic control and automation. A high number of installations have been in operation for many years all over the world; some of them controlling very large network areas and providing an extensive range of functions. At the same time, other areas of application are being covered, like the simulation of operating conditions, the evaluation of different design alternatives, the introduction of artificial intelligence techniques, the maintenance management, the information handling. An overview of the most significant technical experience, existing or in progress, is given for the different application areas. 1 Introduction The last decades have seen a development of the computer-based technologies, certainly well beyond any predictable extent, and interesting almost every field of industrial application. Of course, also the railway traffic control and automation area is now presenting a large amount of successful computer-based installations and it Transactions on the Built Environment vol 34, © 1998 WIT Press, www.witpress.com, ISSN 1743-3509 608 Computers in Railways is interesting to note that they are rapidly increasing, not only from the quantity point of view, but also as far as the type of application is concerned. Less than twenty tears ago an up-to-date traffic control system of a railway line included few basic sub-systems: 1. An interlocking in each station, providing the control of points, signals, track circuits, routes and assuring the compliance to all safety requirements; it was a vital subsystem, based on conventional relays, electromechanical pushbuttons and switches, large mimic display panel, extensive network of inside wiring and external cables 2. An automatic block equipment for train detection along the lines and the control of lineside signals; it was again a vital sub-system, based on electromechanical relays and lineside cables; the train detection was performed by track circuits or axle-counters or loops 3. When available, a kind of continuous or intermittent track-to-train transmission equipment, providing on-board information on signal aspects and an emergency braking under particular conditions (lack of acknowledgement or other irregular operation); it was again a vital subsystem, based on electromechanical components. 4. finally, a centralised traffic control (CTC) installation, for the remote control of interlocking and automatic block subsystems of the whole line (or a section of it) from a central control room, allowing an easier management of the traffic and a significant labour saving; the safety requirement of the operation being assured at the level of the local equipment (interlocking, automatic block, on-board cab signalling), the CTC was a non vital subsystem, using non vital components for data transmission, reception, handling, display. The block diagram in Fig. 1 summarises the allocation of the above sub- systems on a section of railway line. Transactions on the Built Environment vol 34, © 1998 WIT Press, www.witpress.com, ISSN 1743-3509 Computers in Railways 609 Figure 1. Traffic Control System of a Railway line 2 Computer-based CTC In the 70s the process computers and soon afterwards personal computers, workstations and associated equipment appeared on the industrial market. A number of applications were successfully implemented in many industrial environments. The Railways' world, traditionally (and rightly) cautious in the evaluation and introduction of new technologies, first of all considered the possible application of computers to the non-vital portion of the traffic control, i.e. the remote control installations. These installations were already using discrete solid-state circuitry for data transmission and handling, therefore the transition toward the programmable logic was in some way a natural technical evolution. It allowed also significant enhancements in the functions and improvements in the technical solutions: use of video displays instead of the conventional mimic panels, auxiliary indications as train-describer, alarms, etc. displayed by the VDU instead of separate equipment mounted on the mimic panel, extensive data storage in the computers memory, easier introduction of modifications into the system, automatic routing driven by train-describer information, route conflict resolution. In other words, the computer was not only a new modern technological component which replaces an old one; it involved a large enhancement of the functions performed by the conventional CTC installations, which soon became traffic automation centres, with a number Transactions on the Built Environment vol 34, © 1998 WIT Press, www.witpress.com, ISSN 1743-3509 610 Computers in Railways of new additional features both in the traffic control area and also in other ancillary areas, as graphic timetable display, public address information, statistics, auxiliary services control and monitoring, message handling. The IECC Integrated Electronic Control Centre installations currently in operation in UK are an example of traffic automation centre [1]. Similar examples exist in almost all European Countries, as e.g. the Centres of Frankfurt and Munich in Germany, Genoa, Florence, Rome in Italy, Paris for the TGV lines, Folkestone for Channel Tunnel, etc. All the Metro systems have also traffic control centres making large use of computerised equipment for remote control of interlockings as well as other subsystems like electric substations, lighting, public address, escalators, telecommunications, ventilation, fare collection, etc., performing a thorough monitoring of the entire system. A more recent development in this area is the Traffic Supervision Centre, which represents a higher level of traffic control, over the CTC The introduction of high speed lines, the need of improving the competitive edge of the railways against other transportation modes, the performance level attainable through the extensive use of computers and telecommunications are now allowing to build up a network of supervision centres covering vast areas, even beyond the national boundaries. Two impressive examples already in operation are the dispatching centres in Jacksonville, Florida and Omaha, Nebraska, each one supervising a railway network of about 30.000 kms serving a large portion of USA. They operate through a set of existing peripheral CTCs; besides the supervision and remote control of train movements, they also take care of other functions as e.g. the loco drivers' shift management. The European Railways present an almost different situation than the North American ones: high density of traffic, higher average speed, different traffic shares between passenger and freight trains, many national networks with many borders in between. Therefore the traffic supervision in Europe does not cover such very large areas, being generally limited inside the national boundaries; the amount of traffic supervised and coordinated is however very significant, owing to the much higher density of traffic and lines. The Italian Railways have recently awarded the order for a "Network CTC" covering the entire FS main line network (4.200 kms of double track and a dozen of key nodes), which will be controlled by twelve computer-based control centres with a nation-wide connection. The control centres will take over the functions of the existing conventional CTCs and will take care of a set of additional functions, as traffic regulation/optimisation, diagnostics and maintenance data handling, public address, security management. Transactions on the Built Environment vol 34, © 1998 WIT Press, www.witpress.com, ISSN 1743-3509 Computers in Railways 611 3 Solid state interlocking (SSI) For the interlocking the transition from the relay-based circuitry to the computer-based logic was again a natural technical evolution toward new technologies and better functionality. However, new basic problems were met in complying with the safety requirements as specified for the railway signalling vital equipment. As it is well known, the fail-safe requirements in the conventional relay-based systems are fulfilled by means of appropriate measures taken in the construction and in the circuitry, in order to allow a prompt acknowledgement of the failures and at the same time to assure a safe-oriented reaction by the system. This deterministic approach, however, is no longer feasible in an electronic-based equipment, where the reaction to a failure can not be pre-determined during the design of the system. Dozens of papers and articles were published on this subject [2] [3], extensive discussions took place and a number of solutions were proposed and tested. The problem was solved by a probabilistic approach instead of the deterministic approach, in other words achieving the high required safety level by software solutions having an extremely high value of MTBWSF (mean time between wrong side failure). This approach opened the way to the solid state interlocking, whose first installations in the late 70s were followed by hundreds of others in the 80s