HomeRail NewsControl and communications asset management

Control and communications asset management

Listen to this article

Engineering asset management is a collection of techniques, procedures, processes and skills that combine the technical issues of asset reliability, safety and performance with financial and managerial skills.

The emphasis is on achieving sustainable business outcomes and competitive advantage by applying holistic, systematic and risk-based processes to decisions concerning an organisation’s physical assets.

Or, in simple terms, making the most of what you’ve got!

Most engineering disciplines have similar challenges and requirements, and railway control and communications is no exception.

There is a wide range and age of assets and technology, ranging from mechanical interlockings that are over 100 years old to state-of-the-art processor-based products. These assets have to deliver a high level of reliability and safety all day every day, with limited time to ‘switch off’ the assets to monitor, maintain, repair and renew. At the same time, they are competing with other assets for resources and finance.

Successful asset management requires a number of key items including leadership, alignment with organisational objectives, engineering competence, good information, understanding failure modes and innovation.

Asset managers must be strong leaders. They need to have an open mind to new ways of doings things, be good communicators and keep abreast of what’s going on with an ability to listen and be informed. They must have a vision of the future and how to get there.

Plans must be aligned through the asset management objectives, strategy and policy up to the organisational strategic plan. There must be a clear line of sight through all the documents. This will make sure that the assets support the company’s requirements and make investment cases easier to justify.

Engineering competence must be demonstrated and will require a thorough understanding of the principals of rail control and communication systems. Asset managers will normally be charted electrical engineers (CEng) who have had their competence assessed against Engineering Council standards.

Control and communications assets

The control, management and safety of train movements are fully dependent on the control and communications assets. Since the mid-1800s, these have evolved from basic principles into today’s highly complex electronic systems with many different types and technologies across the rail network.


Interlocking of signalling assets with one another prevents conflicting or unsafe train movement. Interlockings were introduced following the Regulation of Railways Act of 1889 and range from the earliest mechanical variants, through a variety of electromechanical and electrical interlockings, up to modern computer- based software-controlled systems.

In total, there are around 500,000 maintainable signalling assets on the network, situated in a wide range of environmental conditions, all of which have the potential to affect train services. These include:

» Signaller’s control systems – enable the signaller to monitor and control the signalling system for the purpose of route setting (using a mechanical lever frame, panel signal box or VDU-based system);

» Interlockings – ensure conflicting routes are not set, as well as monitoring and controlling trackside equipment to assure a safe signalling product;

»  Equipment housings – provide power, communication to the interlocking and an interface to trackside equipment;

»  Points – route trains through a track layout;

»  Signals – pass information to the driver,enabling safe control of the train;

»  Train detection – provides train positioninformation to the signaller and the control system;

»  Level crossings – enable pedestrians and roadvehicles to cross the railway safely;

»  Other assets – including driver’s aids (AWS,TPWS, ATP and trainstops).


A significant part of the control and communications system relies on telecommunications assets to transmit information either between parts of the system or, in the case of ERTMS, between the infrastructure and the train.

With the increasing use of open networks, and the ability for links to be re-routed, the control interface equipment has to provide a level of data security which ensures that messages intended for one part of the signalling system are not misrouted to, or misinterpreted by, other parts of the system.

Cyber security is now a firm requirement for all control and communications systems, and the railway community is now on board with what is required and is learning fast from enterprise networks and other control system disciplines.

Renewals planning

The volume of signalling interventions planned for any given year is primarily influenced by the condition of the asset and its ability to deliver the required outputs, together with any signalling related works to enhance the network.

Many factors, including the availability of track access slots and design, installation, testing and commissioning resources, influence individual project schedules. Interventions can range from like-for-like renewals, through part renewal, to complete renewal and resignalling. Network Rail asset managers are responsible for instigating, remitting and sponsoring the required interventions.


Network Rail maintenance activity is planned and reported at the individual asset level. For planning and delivery of signalling renewals, however, this level is too granular and so renewal plans are considered at a slightly higher level.

The Signalling Equivalent Unit (SEU) represents a vertical slice through the system that is an interlocking area (with all the associated trackside assets). It is therefore a convenient sizing tool for a controllable function, such as a signal or set of points, including parts of the signaller’s control system, interlocking, comms system and apparatus housing in addition to the trackside equipment.

When used for estimating the scope and cost of a resignalling project, the number of controlled functions (SEUs) can be used, along with the SEU renewal rate, to include alterations to them signaller’s control system, the interlocking, train detection, power supplies and associated cabling.

The SEU also includes an allowance for other associated assets that do not themselves constitute a unit. SEU volumes are used to justify budgets and funding requests, therefore it is vital that correct counts are made and recorded in order to make adequate budget provision. SEUs are also used as part of the contracting structure, with a significant effort to improve efficiency, both through scope reduction and a reduction in the SEU rate itself.

The Signalling Infrastructure Condition Assessments (SICA) process provides a structured approach to determining the condition of a signalling asset by answering a set of objective questions regarding its physical condition, environment, reliability and maintainability.

Within an interlocking area, samples are taken of multiple assets (such as signals) and a condition score for each asset type is determined by averaging the score of each asset sampled. This ‘remaining life’ gives an indication of the likely date an intervention is required to renew the asset type based on the currently observed condition, a set of predicted deterioration profiles defined within the tool itself, the currently observed environment and assuming no other interventions are made.


SICA surveys are either primary or secondary – primary surveys are less detailed and occur earlier in the asset’s life. The timing and detail of condition assessments reflects the previously assessed condition, with more detailed and frequent assessments undertaken on those systems in the poorest condition.

A similar system is used for telecommunications assets (with the unfortunate abbreviation of TICA – not for the first time has some wag proceeded it with “Chicken”).

Asset performance

Control and communications assets are integral to how the railway operates and can therefore have a significant effect on train services. Not all failures will affect the reliability of the railway; for example, some components and sub-systems are designed to maintain availability under failure conditions (examples are dual filament signal lamps and duplicated transmission systems).

A longstanding and consistent measure of the safety of the control and communication assets is the number of safety-related or wrong- side failures (WSF) recorded in the signalling incident system (SINCS). These are sub-divided into high-risk events (hazard rating of 20 or more), other failures where the systems are unable to provide some restriction or protection (known as unprotected) and those where the system provides a degree of protection.

Whilst WSFs have, by definition, the potential to lead to a safety incident, it must not be forgotten that any failure of the control and communication system may have safety-related consequences. With the assets designed both to fail safe and to supervise other parts of the infrastructure as well as staff, the result of failure can be to prevent or restrict train movements.

Any loss of the signalling system leads to degraded working – with instructions passed verbally between staff and between signallers and drivers, assuming voice communications are still available. Whilst the procedures are robust, there is always room for human error that can lead to mistakes and incidents.

Control and communication failures have a significant impact on the infrastructure with nearly 40 per cent of all failures attributed to these assets. Failures of points, track circuits, signalling systems and signals have the greatest impact.

The good news is that there is a continuing downward trend in both the number of incidents and the resulting delay. Bringing maintenance in-house, and standardising both the maintenance regime and its application, has contributed to this improvement. Much work has been done to identify and eliminate latent design and manufacturing issues which contribute to poor asset reliability.

Improvements in the performance of signals are largely attributed to the progressive introduction of LED signal heads. For points, the introduction of master-class and supplementary drive set-up training, together with commissioning of remote condition monitoring, and the implementation of improvements to address emerging issues following the Lambrigg accident, have all had a positive impact.

Track circuit performance has improved with the introduction of moulded tail cables, the development and upgrade of TI21 equipment, upgrading older installations to duplicated tail cables, and master- class initiatives to share best practise and improve competency applied to insulated rail joints (IRJ).

Signalling’s traditional failsafe approach – the ability to turn a signal to danger and prevent route setting – doesn’t help availability, and combining high levels of safety and availability within an affordable system is challenging.

Known areas of risk

There are a number of known risks that the asset manager has to be aware of and manage, some of which are:

Wire insulation degradation – the degradation of wire insulation leads to the risk of circuits being unintentionally operated with the potential that train movements are authorised when unsafe. The main causes are excessive temperatures when, in very high temperature environments and with excessive current loading, cables can fail within a few months.

There are no standards or specifications for the lifetime of a wire or cable, although a manufacturer will typically quote in the order of 20 years in the correct environment. Properly designed and managed cables can last well over 50 years, with some of the paper-insulated twisted-pair copper telecoms cables installed in the early 60s still providing excellent performance.

The failure risk with wire degradation is mainly with relay interlockings, but it can occur on all signalling equipment. Certain types of older cabling are known to be at greater risk. Mitigations against wire degradation are environmental controls, regular and automatic cable inspection and testing. It may be possible to replace individual wires one at time, but this can introduce additional risk. Often the only solution is complete renewal.

Silver migration – some insulating materials enable silver, often used in contacts, to form conductive paths through the surface layers of the material. Relay interlockings of older designs, as well as certain types of relays, are at greatest risk although these have now largely been replaced.

Single cut circuits – some lineside circuits only include controls within either the positive or negative leg of the electrical circuit. This simplified design, a legacy of differing approaches to the management of signalling principles and circuit design, increases the risk of protection circuitry being bypassed due to cable insulation faults.

Level crossing approach locking – a legacy of differing approaches to the application of signalling principles has resulted in some manually controlled level crossings without approach locking circuitry. This increases the risk of human error with no safeguards in place. The majority of such installations have now been addressed.

Relay failures – safety relays have a number of known failure modes that, whilst rare, can lead to significantly increased risk such as circuits being bypassed. This can affect all types of interlockings, track circuits and level crossings. Regular maintenance and servicing of relays is required. This is expensive and resource hungry but, as more solid-state systems are introduced, the problem will reduce.

Track circuit rail-head contamination – a particular problem with autumn leaf fall and sometimes with other contaminants such as sand dropped for adhesion. This may also affect rarely used sections due to rust. The problem is best managed jointly with the rolling stock operator and with the assistance of track circuit assisters and wheel scrubbers.

Equipment obsolescence – railways assets are required to have a longer life than in many other industries so equipment obsolescence can be a problem. In some cases, so long as there is no requirement to modify or change the configuration of the asset and spares are available, this is not an issue. It is becoming more of a problem with some very old mechanical assets as engineers with the expertise to manage and service them retire. Electronic software-based systems that are a few decades old can also be a problem. Solutions can require innovation and the input of specialists to retro- engineer parts and subsystems.

Reliability-centred maintenance

Historically, all control and communications equipment was subject to a planned preventative-maintenance cycle designed to maintain the asset in its ‘as built’ condition, or to manage the rate of degradation of the asset to a level that is acceptable.

However, the reliability-centred maintenance programmes for signalling and telecommunications equipment have both identified historic maintenance tasks that cannot be demonstrated to be beneficial either to performance or to the asset and have reviewed the desirable frequencies for the remaining tasks. The benefits of this are that the maintenance resource is utilised more efficiently and, where appropriate, the frequency of visits is adjusted to match the criticality of the asset. An example is two sets of points, one outside a very busy station which moves hundreds of times a day, and a lightly used set on a lightly used route which is only used occasionally. Do they require inspection and maintenance at the same frequency? The answer is no, and the more intensively operated set should require more.

The asset manager is responsible for endorsing and approving any change to maintenance plans and monitoring that the change does not adversely affect the performance of the asset. The Network Rail asset manager also manages a team of specialist engineers that assists and mentors the maintenance technicians as well as carrying out independent competency assessments.


Intelligent infrastructure

While processor software-based systems can be a problem with early obsolescence, the same technology, together with modern communications, has provided the ability to monitor the condition of assets remotely. Intelligent infrastructure and the Internet of Things (IOT) will take this to another level, with even more information available to assist the asset manager. In the future, this may include automatic input into the SICA system and to request maintenance interventions.

BIM and other integrated asset information systems are also useful tools, but these need to be carefully designed and integrated to reduce manual input and interpretation, avoid duplication of effort and to provide only one version of the truth.

Where substantial numbers of assets within an interlocking area are assessed as life expired, or there is a need to change the operational configuration of the assets, then an interlocking area approach is adopted.

Projects are categorised to include conventional resignalling (where the interlocking and all associated assets are renewed and reconfigured, often with an update to, or replacement of, the signallers control system) and level crossing renewals (including alterations to associated signalling assets). Typically, the opportunity will be taken to incorporate network enhancements and introduce operational efficiencies by combining control areas. This will increase with the introduction of ETCS and traffic management.

Historically, the rate of renewal of SEUs has been about 1.5% of the population per annum, indicating that many assets are being retained in service for over 60 years. So the asset manager has a very challenging, but important and rewarding, role – one that is vital to getting the most out of the railway’s control and communication assets.

Written by Paul Darlington


Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.