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The connected asset – when a cab radio is not (just) a cab radio

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The railway of today faces many challenges and these include the need to reduce costs, improve operational efficiency, and improve passenger / freight customer benefits. The industry needs to make the best use of the assets already invested, and providing reliable data connectivity for trains can deliver huge benefits for operators and customers. This article discusses how the GSM-R cab mobile asset, already fitted to main line train fleets in Britain, could be used to meet these objectives.

Railways consist of a huge number of assets which must all work seamlessly together to deliver a good, consistent service to passenger and freight customers. Every asset will show signs of wear and tear over time. These signs will appear differently depending on the type of asset, how it’s used, and what components fail first. Maintainers and asset managers won’t always notice changes in conditions or be able to associate these with particular hazards or failures. However, connected remote condition monitoring can provide information on how asset condition measurements on both trains and ground systems are changing over time, and allow interventions to take place before failure occurs. To achieve this requires a good train data connection.


Fitting new communication and control technology equipment to existing rolling stock is a challenge. First-in-class train fitments can be costly and not run to programme. Any new device will need space on the train, connection to an existing reliable power supply, an interface to on-board systems, an external antenna causing no interference or compromising the vehicle integrity, and a means of sharing information with train staff. No two types of rolling stock design are the same and each will have its own peculiarities and limitations. Any fitment programme will take valuable trains out of service and require a competent resource to plan and undertake the work. All of this takes time and money the rail industry cannot afford.

Siemens Mobility SVR-411 V4 cab radios, however, have already been fitted to all of the British main line fleets by the GSM-R project, providing reliable, secure track-to-train voice comms’ across the network. This required many years of engineering to provide a space-efficient, robust, and flexible cab radio rack in the space available, together with a compact control panel unit for the use of train drivers. A little-known fact to many in the industry is that the Siemens cab radio hardware / software is designed and made in Britain, so all the knowledge and capability to support and enhance the product is readily available. To date, over 12,000 cab units have been fitted to trains in Britain and the technology has also been successfully deployed in other countries including Denmark, Australia, Ireland, and Norway.

The design of a unit to allow the scale of deployment achieved by the GSM-R project required a special ‘gland box’ system to allow easy installation and replacement, and the development of an optional uninterrupted power supply unit to provide up to four hours backup power in the event of failure of train power. Two versions of the unit were originally created, one to provide voice communications only, the other to enable ETCS L2 data connectivity with the ground system. The very high availability requirements were met by a design which provided good thermal efficiency and shock resistance. The mean time between failures currently runs at around 250,000 hours, and the mean time to replace a unit is around 30 minutes. In Britain, a textual display is used to provide the human machine interface, but a full graphical unit is also available if required.

So, we have a successful product sitting on practically every train in the country, but what else could it do?

DAS DCP showing DAS msg.

Digital connectivity

Rail Engineer first reported on using the GSM-R cab mobile to support Driver Advisory Systems (DAS) and other applications in 2016, along with how the cab mobile would need to be enhanced to provide additional connectivity and functionality. GSM-R was originally based on 2G ‘voice only’ connectivity, and the limited bespoke data connection was only for the setting up of calls and very limited text information for the driver. GSM-R radio coverage has been provided along all Network Rail routes with the provision of over 2,400 base-station sites with heights between 15-29 metres (50-100ft), and 350 repeater sites, covering tunnels, cuttings, and other areas such as stations. Public 4G Long-Term Evolution (LTE) radio will not cover the rail network in the same way, however it is surprisingly good on some rail routes and in some parts of the country, but only if a good, efficient train roof top antenna is used. 

Obvious signal blockers for public 4G are deep cuttings and tunnels. Trains also run through rural areas with few villages, towns, or roads and therefore little public mobile coverage. With busy trains carrying the equivalent of a small village-worth of people, all attempting to connect to their nearest mobile operator’s base station from inside a ‘Faraday cage’, public mobile coverage on trains can be poor. A Faraday cage, to which modern trains can be likened to, shields its contents from electromagnetic fields, such as radio signals. So, when a radio signal hits the cage, the electromatic charge remains on the outside rather than travelling inside.

In 2020, Transport Focus found that train passengers only receive a good 4G connection some 58% of the time. However, using a good, efficient train roof top antenna can dramatically improve coverage, compared to inside a train, and Siemens has developed a new multiband antenna called SMBA (Siemens Multi-Beam Antenna) to provide reliable GSM-R/ 4G / GNSS / Wi-Fi connectivity, all within the footprint of the original GSM-R train antenna.

The cab mobile has also been enhanced to provide GSM-R, 4G LTE, GNSS/GNNS, Wi-Fi, and with SD & SSD memory cards for other applications. A Secure Digital (SD) card is a compact and removable storage device with extensive capacity, and a Solid State Drive (SSD) is a faster alternative to the old storage hard drive. Accelerometer functionality has also been integrated into the processor module along with optional 4G modules. All this functionality seamlessly connects to the external antenna, and the processor card supports all the main features for an extensive application platform with reliable connectivity. The cab mobile is no longer 2G ‘voice only’.

The British roll-out of the GSM-R cab mobile system started in 2009 and all the units have since been upgraded with the additional functionality. The creation and installation of the mobile cab radios led the Siemens team to realise that having overcome the major challenges of on-board installation – space, power, interfaces – there was an opportunity to provide a range of new functionality inexpensively, and with minimal impact on train fleet availability.

In a similar manner to other items of modern electronic equipment such as smartphones, by developing ‘apps’ to run on the additional SVR-411 processor, affordable new functionality and improved operational efficiency can be provided in a number of ways.

Train Borne Condition Monitoring

The first ‘app’ to be developed by Siemens used the in-built GNSS capability and three-axis accelerometers within the radio to continuously monitor the train’s ride. This is known as Train Borne Condition Monitoring (TBCM).

Trials in the South West of England have demonstrated the system can reliably pinpoint areas where there are voids under switches/crossings and on plain track, which can be used by the maintainer and asset steward to prioritise further investigation and plan the appropriate intervention. TBCM can also identify areas of ‘rough riding’, especially if reported by several trains passing through the same part of the network. ‘Dip track’ locations, which can ultimately result in derailment if not detected and mitigated, can also be identified.

By adding this functionality, every train can continuously monitor the state of the track, and communicate the status back to the maintainer / asset steward to instigate an intervention in real time, without the need for anything other than a new plug-in card and a software update.

Connected Driver Advisory System

Connected Driver Advisory System (C-DAS) allows calculated information to be continuously sent to train drivers. The important difference to Standalone Driver Advisory System (S-DAS) is the connectivity aspect and having a real time data link between train and trackside, so schedule updates on disruption are automatically sent to the C-DAS for use on-board. With S-DAS, the system stops operating when the train is running significantly off-timetable due to disruption. Another example would be platform changes, the signalling system may have to route a train into a different platform than planned due to another train running late. C-DAS can keep up to date with the new route as well as any changes in line speed and speed profile due to the different route.

Some may think C-DAS takes responsibility away from a driver, but this is not the case and (as the name suggests) C-DAS only ‘advises’ a driver. A competent driver is still required to control the safety critical aspects of the train. Several successful C-DAS applications have been created and used on several railways across the world. Generally, for new C-DAS, it is necessary to add new on-board processing and communication equipment, as well as driver machine interfaces to convey information to the drivers. However, with the cab-mobile version of C-DAS, the mobile radio’s connectivity is used to exchange data with the ground system using 4G.

The minimum requirement is to upgrade the existing GSM-R antenna with the SMBA that supports 4G LTE and GNSS/GPS as well as GSM-R. This would use the existing four-line GSM-R display, but a graphical display to provide additional information in addition to just train speed is available. This is easy to install as it reuses the existing location of the standalone S-DAS display via an adapter bracket. Trials of the system have demonstrated fuel savings of typically up to 15%, which is a very strong business case for activation of the app.

The main benefit of C-DAS over standalone or networked DAS is the connectivity to the C-DAS trackside server to ensure the driving advice is automatically based on the latest operational plan. One challenge is that there is no common railway location referencing scheme in Britain used by all the sources of data C-DAS requires, so the trackside software must map between them, for example:

Temporary Speed Restrictions (TSRs) and quarter mile post locations (to display the current location to the driver), which use Line of Route (LoR) and Engineers Line Reference (ELR).

Schedules and schedule updates, which use Timing Point Locations (TIPLOCs) that are areas such as junctions and stations, as well as line in and path out codes.v

Data on static speed, gradient and signal locations (for train describer berths) from scheme plans, which use meters from a datum.

Track centrelines, which are GNSS Latitude and Longitude polylines to allow the C-DAS on-board to map it’s GNSS location of the train to the schedules, TSRs, and the static speed profile and gradient profile of the track ahead.

The national passenger information system, Darwin, provides schedule updates that C-DAS can use in areas without a suitable deployment of Traffic Management (TM). Darwin adjusts the schedule timings for late running detected by the train describer stepping feed, and shares any platform changes from the baseline timetable entered by operators. TM plan/re-plan systems aim to optimise the overall current plan of train movements to an agreed Key Performance Indicator (KPI), allowing plan changes to be tested first in a sandbox environment and the evaluation of knock-on impacts between trains, before commitment.

Where TM is deployed, it is important that C-DAS makes use of the TM published schedule updates, via the Network Rail Layered Information Exchange (LINX) system. In some scenarios, this would provide earlier awareness of any plan changes, which C-DAS could use to advise a reduction in speed further in advance than with a later Darwin update, potentially saving even more energy. This also ensures the C-DAS driving advice is based on a current plan, consistent with what is being fed to the Automatic Route Setting (ARS) systems controlling the signalling route setting.

Cab Radio Management Terminal

Another system functionality app that has proved useful is the Cab Radio Remote Management Terminal (CRMT), which allows the management of cab radios remotely via an IP connection.

Using the radio’s in-built connectivity, a whole fleet’s set of cab radios can be monitored, with everything from versions and serial numbers through to error logs being accessible remotely.

Software can also be updated remotely, along with phone book entries and message templates. The implementation of CRMT removes the need for a technical visit to the train, improving efficiency and reducing the cost and risk that every train visit entails.

Future app capabilities

With the cab radio now effectively becoming a mobile communications gateway, many other apps can be provided for other systems on the train using the SMBA 4G LTE capability and Ethernet network interface.

Currently under development are solutions that allow remote public address announcements to be made to trains or groups of trains for enhanced passenger information. Timely accurate passenger information can help to keep passengers who face delays informed so they can plan ahead. Having a journey disrupted annoys passengers, but knowing why their journey has been disrupted, what is being done to resolve things, and what their options are, can all help to maintain their confidence in rail.

The cab secure radio system which preceded GSM-R also had a train public address link, but it only allowed the signaller’s radio dispatcher to make train public address announcements. The problem was that signallers are not trained, or do not have the time, to make public address announcements, and it was only used in emergency situations.

With the GSM-R cab radio app, a secure IP connection can easily be provided to any train operator’s GSM-R dispatcher or automatic public address system. 

Future communications potential

Whilst the original 2G GSM-R has performed well for many years, the need for a new communication technology is driven by the obsolescence of GSM-R, and the move to 5G-based communications is essential to provide the voice and data communications which the railway will need from 2030 onwards. The replacement of GSM-R with Future Railway Mobile Communication System (FRMCS) is still some years away and will take some time to implement, so each of the app ideas are important for deployment now.

From 2030, however, the implementation of enhanced radio solutions with FRMCS will offer the potential for an even greater step change in train and trackside service integration. Siemens says its  GSM-R cab radio platform is capable of being upgraded to use FRMCS, so any investment in the cab radio should not be wasted and FRMCS will see faster, more secure, and more reliable communications which can be exploited in future applications.

The train-borne apps of today will be superseded by solutions that can benefit from more bandwidth, for example video systems to monitor passenger spaces, and allow higher grades of automation. Far more data from the complex ‘system of systems’ that will make up new rolling stock will need to be transmitted back to control centres, so that data can be integrated with information from a multitude of trackside systems to provide a system-wide integrated view of the railway. The railway of the future will see connectivity and data as critical to a smooth, efficient, and reliable network, which is the obvious choice for travellers. This can only happen if rail can be made affordable and make the best use of the assets it already has.

A crucial step

Futureproofing technology is critical if the industry is to keep up with the rapid change of system technologies, especially in areas like communications; but it is possible to mitigate the impact of both obsolescence and technology change. A lot of time, effort, and money has been involved with fitting GSM-R equipment to trains. The experience of providing additional functionality to the on-board cab radio has demonstrated that it is possible to build on this investment, to add additional capability in an inexpensive and non-intrusive way, and be a step to FMRCS.

Image credit: Siemens Mobility

Paul Darlington CEng FIET FIRSE
Paul Darlington CEng FIET FIRSEhttp://therailengineer.com

Signalling and telecommunications, cyber security, level crossings

Paul Darlington joined British Rail as a trainee telecoms technician in September 1975. He became an instructor in telecommunications and moved to the telecoms project office in Birmingham, where he was involved in designing customer information systems and radio schemes. By the time of privatisation, he was a project engineer with BR Telecommunications Ltd, responsible for the implementation of telecommunication schemes included Merseyrail IECC resignalling.

With the inception of Railtrack, Paul moved to Manchester as the telecoms engineer for the North West. He was, for a time, the engineering manager responsible for coordinating all the multi-functional engineering disciplines in the North West Zone.

His next role was head of telecommunications for Network Rail in London, where the foundations for Network Rail Telecoms and the IP network now known as FTNx were put in place. He then moved back to Manchester as the signalling route asset manager for LNW North and led the control period 5 signalling renewals planning. He also continued as chair of the safety review panel for the national GSM-R programme.

After a 37-year career in the rail industry, Paul retired in October 2012 and, as well as writing for Rail Engineer, is the managing editor of IRSE News.


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