State of the Art of Computer Application to the Railway Traffic Control and Automation Giuseppe Sciutto* & Giacomo Astengo

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

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 subsystems on a section of railway line.

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

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.

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 and 90s in Europe, in USA and in the Far East.

The advantages of SSI are well known: modular architecture, no parts subject to wear and tear, reduced space requirement ('from a ball- room to a cupboard'), less outside cabling by appropriate location of peripheral units, easier interfacing with other computer-based systems (CTC, public address, data transmission), easier introduction of modifications.

4 Automatic Block

The considerations under the previous chapter about interlocking are in principle applicable to the automatic block equipment. However, the limited quantity of relays and other conventional equipment required by each automatic block signal operation does not justify their replacement by a computer-based architecture, which would in general result much more

612 Computers in Railways

costly. Hence the need of concentrating the equipment in few lineside locations or directly in the adjacent interlocking. The same consideration is equally true also for the small interlockings, whose functions can be transferred to the computer-based interlocking of a major station nearby. This solution is broadly applied to the metro networks, where the station are generally small and short-spaced each other.

5 On-heard computer

In the last two decades the amount of information conveyed on-board the locomotive by the track-to-train transmission is dramatically increased. Initially limited to few basic signal aspects, the information content has been quickly enhanced to include location data, target speed value, target distance value, line physical data (gradient, max allowed speed, level crossing, curves), permanent/temporary speed restriction orders, etc.

The European intermittent track-to-train transmission equipment (Eurobalise), recently approved as European standard, provides the supply of 1023 bits at every transmission beacon (balise) encountered by the train. Furthermore the ATP (Automatic Train Protection) function requires a continuous comparison between the train speed and the allowed speed diagram generated from the information received on-board together with the automatic warning and braking action should the driver not obey the target instructions.

It is clear that the handling of such amount of information and the implementation of the ATP function requires an on-board computer-based intelligence, complying with the usual safety requirements and also assuring a high level of reliability/availability in spite of the difficult environmental conditions existing on the locomotives. The on-board intelligence has also to take care of other functions, like the man-machine interface (MMI) for the driver, the operation data recording, the radio communication between driver and ground and, when required, the Automatic Train Operation (ATO) and other auxiliaries (passenger information, door control, closed circuit TV, ).

Computers in Railways 613

6 The future prospects

The previous chapters give an overview of the areas where the computer based technologies are replacing the existing conventional equipment based on relays and other electro-mechanical or discrete electronic components. It should be noted that the replacement has brought a very significant improvement in terms of cost, space, reliability, operation speed, number and extension of functions The computer technology continues to progress very quickly, every year new products with higher performance appear on the market, often at lower price and lower space requirements. It is therefore easy to foresee that the replacement process of the old equipment will continue, whilst the new lines, especially the high speed/high capacity lines, will be equipped with high performance and highly sophisticated control systems. The next step forward is clearly the fully integrated railway control system, where the on-board intelligence, the interlockings and the control supervision centres will address the railway as a whole, not just a collection of separate disciplines [4].

7 The Artificial Intelligence developments

An innovative line of development, applicable to railway traffic control, is to be mentioned: artificial intelligence and expert systems. As a matter of fact, a railway system, owing to its nature of fixed guideway and mass transportation means, relies on highly organised structures, like the centralised control, the traffic regulation rules, the timetable-based operation, the staff duty scheduling, and so on. The use of artificial intelligence and expert systems techniques in the traffic management enables the decision making process to take into account the past decisional experience together with the current operation parameters: the result is the optimisation of decisions, the cost reduction, the efficiency increase, the better quality of service. Many areas can take advantage of this approach: the emergency management, the maintenance, the energy saving, the staff duty scheduling, the intermodality management. The emergency management is particularly important in a rail transportation network, especially in those having high traffic density like metro systems or commuter lines. Problems of delays, overcrowding, failures are quite common and can have dramatic impact on a large area unless appropriate measures are quickly taken. Experience shows that the operators could be negatively influenced on such circumstances by

614 Computers in Railways

emotional pressure and need of doing something anyway. An interactive guideline instrument like expert system supplies the operators with the current operation data associated to a knowledge-base of the past experience.

A number of studies and experience are reported in papers of the previous Comprail meetings and elsewhere [5] [6] [7].

8 The simulation tools

The impressive progress in the computer technique has made available a widespread range of simulation programmes, running on standard personal computers. They simulate the train circulation on a railway network, allowing to change practically all parameters during the simulation: network layout, type and location of signalling, block section location and length, train operation data (speed, acceleration, braking), line physical constraints. It is therefore easy to evaluate the cost and performance of different technical alternatives and choose the most suitable to meet the requirements. The modular structure of the programmes allow to modify the functions or to provide additional features.

References

[1] R. C. Nelson, Yoker Integrated Control Centre, IRSE (Institution of

Railway Signal Engineers) Proceedings 1986/1987, p. 134

[2] K. H. Wobig, Modern technologies in Fail-safe systems, IRSE

Proceedings 1986/1987, p. 21

[3] C G. Shook, Microprocessors in Fail-safe systems, IRSE

Proceedings 1986/1987, p. 31

[4] Eddie Goddard, Presidential Address, IRSE Proceedings 1995/1996,

p. 16

[5] G. Astengo, C Rossi, G. Sissa, An Underground Traffic Planning Expert System, COMPRAIL 1990.

Computers in Railways 615

[6] H Schaefer, S. Pferdmenges, An Expert System for real time train dispatching, COMPRAIL 1994 (Computers in Railways IV), Vol. 2,

page 27

[7] A. Fay, E Schneider, A knowledge-based decision support system

for high speed maglev train traffic control, COMPRAIL 1996 (Computers in Railways V), Volume 2, page 3.