Railroad Engineering: Systems and Communications





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1. Getting things done!

In this guide, thus far we have concentrated largely on the material things which together make up a railroad. We have considered how they have evolved thus far, how they perform, how they interrelate, how they degenerate and how they are eventually replaced.


Above: Second Avenue Subway project (New York) rendering

Understandably, engineers in all disciplines tend to concentrate on their particular area of the material components, perhaps sometimes giving less attention to non-material considerations.

This section therefore looks at the 'people' aspects of railroad engineering, including systems of working and means of communicating between people both within the railroad organization and to passengers and the world at large outside.

Systems engineering looks at the whole process that is involved in producing something. To make any progress, it is necessary to break down the complete system under consideration into its component parts (subsystems) and then to examine each in turn, breaking down further until the required degree of simplicity has been obtained.

However, just looking at the various component parts will not enable the whole system to function. To achieve this, each part must 'talk' to one another. The path by which this occurs provides the interface between two subsystems. Identification of these interfaces is crucial to the system as a whole.

It is in this area that humans tend to be the weakest. In particular, the interface between human processes and between human and machine actions are where most errors are introduced.

2. Human processes

In human processes, a useful way of looking at what happens is to consider as well as the various inputs that feed into the process and the outputs that are expected, any constraints and supporting services that are needed.

Such an approach helps understanding of the way that the process can be executed and, by identifying the necessary inputs, constraints and supports, forces the system designer to consider all the factors that lead to outputs.

On early railroads, many systems were introduced informally as experience was gained, to fulfill certain basic engineering functions. Often where railroads were simple or limited in layout and unsophisticated technically, one man or group of men would be responsible for most aspects of one basic component or part of the infrastructure and there was no need to work out a system as such.

A good example of this would be the permanent way lengthman or 'ganger' who would know his length of track intimately. He would also consider that it was his job to walk the track, inspect it, carry out daily adjustment, repair locally and replace broken components when he deemed it necessary.

As time went by however, many such functions began to be carried out by different individuals and even by different organizations. In the case under consideration, track inspection, day-to-day maintenance and track renewal over the whole of a railroad layout might be carried out by different organizations with different plant available. In that case, a system needs to be devised with proper communication between parties.

3. Good feedback

The simplest systems have a process that acts upon the input and produces an output according to a set procedure. Such systems only work if completely mechanistic as the output will differ according to any change in the process or any disturbance to the process from outside. By constantly comparing the output with the desired state, any error can be detected and put right.

This feedback of what is happening enables the process to be self controlling.

An understanding of the nature of feedback is essential to predict the effects that it will have. Although theoretically better than open loop systems, if the nature, timing or amount of feedback is wrong then the result can be to over correct the error.

It is important to remember these simple facts when designing control systems. A good example of this is that of a railroad controller operating with poor communications. If the situation being described to him does not reflect reality, either because the observer is only seeing part of the picture, or is exaggerating the true position, or even if the time that the message has taken to reach the controller is such that the situation has then changed, then the action that he takes may well be less than the best and possibly even make the situation worse.


FIG. 1. Open and closed loop systems. Control Theory; Open loop system

4. Interface between operation and engineering

Probably the most important interface in any railroad organization is that between operation of the train service and the engineering back-up. It cannot be stressed too often that the 'raison d'etre' for any railroad is to carry passengers and/or freight and is primarily neither to 'play trains' nor to practice engineering. This said, it follows that there needs to be close co-operation and support between operators and engineers in all areas if the primary railroad objective is to be met.

Within the railroad operational organization, there are likely to be interfaces between overall control, line control and station or local control and, as has been already pointed out, good communication and feedback is essential.

The same applies to the interfaces between engineering and operation at all of the control levels.

In the past, there was a great deal of face-to-face informal communication between men 'on the ground' and problems were often solved locally by individuals who knew and respected one another. In the days when local manual signal boxes were close to stations and shunters' and trackmen's cabins, individuals would quite often meet in the box and agree action that should be taken, as and when the need arose. In this local arrangement, the interfaces between operating and engineering were usually adequately covered. There is one word of warning however, that must always be kept in mind when extolling the virtues of local face-to-face problem solving.

Local problems may well have wider effects and the best overall solution may be different from the one that only deals with the local situation.

As railroads have become less labor intensive however, and control more centralized, local interfaces have become more remote and good means of communication therefore become even more critical. This communication must be both horizontal, to all parties at the same level, and vertical, to other levels of control.

5. Interface between operator and user

Communication with the passenger or customer is also very important so that they may be kept aware of the situation and appraised of any likely variation to the service for which they have paid and can rightly expect to receive.

6. The railroad systems pyramid

Control of a modern railroad can be seen as a pyramid of systems.

The signaling system extends from the train to the trackside and to the central control room. Similarly the other systems that assist in controlling the railroad and informing/directing passengers or customers can be thought of as part of this pyramid of control. Each system is an integral part of the control of a railroad and consists of equipment and operators, the material and human aspects of control. Backing each operational system is the engineering required, including the vital maintenance, fault finding and central diagnostics that is an essential part of the on-going engineering service.


FIG. 2. The systems pyramid.

All the various systems that work together to control a railroad system, and ensure the best possible service, have both interactive and automatic effects on the railroad system as a whole. These effects can be obvious, formal and immediate but many others may be less obvious and will take time to make their effect known.

A good example of the latter is bridge inspection. If bridges are not inspected properly, then some essential maintenance may not be picked up and conditions could deteriorate. However, a perfectly good service could continue to run and it might be years before conditions degenerate to such an extent that services are effected.

The main systems that need to be put into operation, which directly affect and assist the day-to-day operation, will include those listed in the following sections. Each railroad must also ensure that adequate systems are put into practice in all other areas to ensure trouble-free operation in the longer term.

7. The railroad signaling system

To be able to safely and efficiently control any railroad, there must be an adequate signaling system. The technical details and evolution of railroad signaling is covered in Section 10 of this guide.

In basic terms, railroad signaling has two prime functions. These are firstly a means of control of the railroad and secondly a means of providing operational information to locations, equipment and individuals to enable appropriate action to be taken.

A fully comprehensive signaling system on a complex layout should provide the following data automatically:

  • Train regulation to keep within timetables.


  • Train description and route setting.


  • Staff protection.


  • Full protection of train movements.


  • Automatic Train Operation [when installed]


  • Automatic Train Protection [when installed]

With these, the following interactive information should also be available to the appropriate level of control:

  • Information about service disruption.


  • Train service reports, history/graphing.


  • Early prediction of possible problems and operational conflicts.


  • Train and crew positions.


  • Arrival time predictions.

* Local data on signals and speed codes.

Each railroad operational organization will need to agree, with its engineering back-up, the levels at which this automatic and interactive information is to be provided and at what level appropriate action will be taken. The means of control will vary widely from a timetable modification, which could affect a whole line, to a local route modification only affecting two sets of points.

8. The public address system

Once potential passengers enter railroad property, the railroad authority has a duty of care towards them to ensure, as far as possible, that they travel safely and reach the destination for which they have paid their fare.

The various stages of this process including where and how to purchase a ticket, what route to take to which platform and where to alight, can usually be covered by fixed notices, maps, platform indicators and other publicity.

From the earliest days of railroads however, it was found that it is essential also to have some means of communicating with passengers before and during their journeys. Perhaps the most frustrating experience for any passenger is to enter an unfamiliar environment and not be able to find out where to go for the train or, having found the right platform, to be unsure which train is the correct one.

Almost as bad is an inefficient, echoing or otherwise inaudible public address system which only confuses or frustrates rather than giving clear understandable information.

On any modern railroad system, whether it is main line, suburban, metro or light rail, there must be an efficient and audible public address system.

At the planning stage of any new railroad or large interchange station this subject needs to have the very careful consideration of both the operators and the engineers concerned.

Experience has shown that in large public areas, it is far better to have a large number of small speakers placed at a fairly low level than a smaller number of high level or high powered speakers.

Good public address facilities enable network-wide messages to be sent from a network control center, a line control office or just to passengers on one station or platform either from the center or from the local station control.

Public address systems are the principle means of controlling passengers and should be used on platforms and circulating areas to control passenger flow, assist train boarding and evacuation when emergencies occur.

These facilities are absolutely crucial in dealing with any emergency and railroad authorities should consider carefully what arrangements should be made for automatic pre-recorded instructions for evacuation if there is no response from control rooms or local operators, in the event of fire being detected.

Discussion between the railroad authority and local emergency services for dealing with such emergencies should include the proposed use and control of all public address systems.

9. Phones, radio, broadband

Voice contact by phone has become so much part of our ordinary working, family and leisure lives that it is hard for us now to imagine how people managed without it.

It is well, however, to remember that passenger railroads had been operating successfully for almost half a century before Graham Bell's new telephone began to be accepted as a reliable means of communication.

Electric telegraph, in various forms, began to be used to a limited extent on some railroads from the 1850's, but this was a slow letter-by-letter method of transmitting messages often based on the Morse Code which was not known to all railroad men.

By 1860, this cumbersome method gave place to a simplified system in which an electro-magnet could hold a single steel needle deflected to right or left pointing to an indication 'line clear' or 'train on line'. If no current was passed to the instrument, the needle would remain vertical indicating 'line blocked', thus making the system 'fail-safe'. With the introduction of this simple electro-magnetic system, the first instant communication between signal boxes became possible and the 'block telegraph system' was established. Telephones with hand cranked bells were installed later but were not considered 'fail-safe' and were an additional aid to the signal man rather than a replacement for the block telegraph instruments and bells used to communicate the position of trains from box to box.

Today, smartphones and broadband are used extensively to communicate information throughout a railroad system and to the passengers and other customers.

Consideration needs to be given to security of supply to important phones, particularly, if they are provided by an outside telephone authority. Alternative lines supplied from a separate power source should be provided in all control rooms and other vital control locations both linking with each other and with the emergency services.

The possibility of an incident on a railroad severing power and telecommunications cables needs to be addressed. Some degree of protection in this respect can be given by ensuring that power, signal and telephone cables are sited in different cable runs and ducts, preferably on different sides of the track or tunnel.

Most railroads have an extensive internal telephone system with telephones in all control rooms, signal boxes, station operations rooms, on each platform and at many signals. However, those working on or about the railroad are often remote from telephones and, before radio, had to walk long distances to report incidents, progress on works or give up possession.

Radio is now the principal means of communication and control for those staff who cannot easily get to a telephone.

Radio is used as a means of communicating with train drivers and increasingly, with station staff, police, ambulance and other emergency services.

The use of 'pagers' and other personal radio communication links can be invaluable in contacting 'on call' and other key personnel when incidents occur.

It is vital to ensure that all radio systems used by the railroad and emergency services are compatible and that the various command and control structures can communicate in all eventualities and operational locations.

10. Closed circuit television

CCTV provides a very useful feedback mechanism enabling control rooms and the emergency services to gauge what is happening on the ground.

In particular, CCTV enables controllers at stations to manage flow of passengers and to prevent dangerous overcrowding situations to develop.

By introducing video recorders, CCTV enables analysis of events which can lead to future improvements. In the event of crime being committed, it can also prove extremely useful in detection and obtaining prosecutions.

CCTV on platforms enables drivers to see passenger movement onto and off trains and to decide when doors may be safely closed.

On unmanned stations, CCTV cameras on platforms, by ticket machines and at other strategic viewing locations enable close scrutiny of passenger movements from the control room. In conjunction with the use of the public address system, this can be a very powerful tool in dealing with vandalism and other misbehavior. CCTV has been particularly useful on light rail systems with frequent unmanned stops.

With a complex system and large interchange stations, the task of watching a large number of CCTV monitors becomes at the same time daunting and very boring. Much care needs to be given to the arrangement of this in the control room to ensure that the best use of the equipment is made both during normal working and at the time of incidents. As has been said previously, the interface between the machine and human intervention is the weakest and needs to be addressed if the full potential of the 'hardware' is to be realized.

11. Equipment operation and system maintenance

Traditionally, on most railroads the responsibility for the maintenance of fixed engineering equipment on railroads has been left with the relevant engineering departments. Bound up with this has been first hand knowledge of the state and operational mode of various pieces of equipment. Generally this has worked reasonably well, but it can lead to frustration on the part of an operator faced with a crisis situation if he is unable to reach the 'man who knows'. Increasingly, systems are being introduced on modern railroads to monitor the operation of critical parts of the railroad equipment infrastructure. The objective of this is not in any way to move responsibility for maintaining equipment from the right quarter but to give information to both operating control rooms and engineers to enable them to make rapid decisions when incidents arise. This is particularly important when unexpected things happen which could develop into a life threatening situation.

In particular, the hazards of fire, smoke and flooding are influenced by the operation of certain critical pieces of equipment, including the following:

  • Escalators, elevator/lifts


  • Pumps


  • Sump level indicators/cut-outs


  • Fans and louvres


  • Automatic alarm systems


  • Flood containment doors and barriers

Monitoring should indicate at all times whether or not each piece of equipment is actually working and in what mode (e.g. up or down, pressure or exhaust) and if not working, whether or not it is capable of working or is down for maintenance.

In the case of a train on fire producing dense smoke in a tunnel, for instance, the Controller needs to know quickly the mode of operation of any fans in nearby vent shafts before deciding which way to detrain any passengers in other stranded trains.

A co-ordinated approach is needed to keep all these various systems running. Ideally everything from the state of the train equipment to the preventative maintenance of an escalator should be visible to the maintainer and his manager.

Especially in the case of an emergency, the quality, accuracy and promptness of the information given will largely determine the quality of the response and the resultant 'down time' of the railroad.

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