The National Radio Network, originated by British Rail, has finally been switched off. It served the railway well for over 40 years and provided a significant contribution to improving communication between people in many forms during its lifetime. It is therefore appropriate to record the NRN history and to set down some of the achievements that resulted during its lifetime.

From a personal perspective, I had the task of creating the network (then called the National Radio Plan – NRP) in 1973 and built up the radio team at BR Headquarters that was to design and implement the technology. There were many political, administrative and technical hurdles along the way and it took a persistent and concerted effort for these to be overcome. The NRN had a number of engineering changes during its life and also a significant change of use.

Early days

During the first decade and a half of British Rail, regional dominance was the order of the day and schemes to develop technology as a national perspective made little headway. Radio usage largely consisted of small local systems to give voice communication between staff working at major stations and freight marshalling yards (including communication to shunting locomotives). Some of the more adventurous regional engineers had visions of building wide area radio coverage networks but little progress was made which, with hindsight, was no bad thing since every region would have done it differently.

A common problem in those days was how to communicate with engineering staff engaged in trackside work when they were required elsewhere if an emergency arose. A number of lineside call systems were invented, some using either lights or loudspeakers mounted on equipment cabinets that emitted different calling signals depending on the department required. These were of limited success and something more resilient was required, radio being the obvious choice.

Thus agreement was given that a national radio based communication network should be investigated and developed to give universal coverage throughout the BR domain. Under the inspired leadership of John Boura, the head of telecoms engineering at BRHQ, the NRP group was established and I was brought down from the Midlands as its head. As well as assembling a London-based team, a working party involving radio experts within the regions helped to unify thinking and generate a spirit of co-operation.

Setting the scene

Defining what the NRN should and should not do was an early challenge. Remember that, in those days, the public cellular mobile networks did not exist but several industries (fuel, power and the emergency services) had established wide area radio coverage. How had they achieved it and what technology was used?

Getting an allocation of radio frequencies was the first objective and this involved difficult negotiations with the Home Office, which was then responsible for spectrum management. VHF frequencies offered the best practical solution but nothing was available in the low band (80-90MHz) or high band (150-160MHz) parts of the spectrum. Under pressure from rail and other industries, a VHF mid band was created offering 105-108MHz for mobile transmit and 138-141MHz for base station transmit, this becoming known as Band II. The 33MHz separation was a problem for aerial efficiency but at least it was a start and an allocation of 12 channels was achieved.

Another vexed question was whether to use Amplitude or Frequency Modulation (AM or FM). Each had its diehard advocates, both within the railway and the supply industry, but a decision to adopt FM aligned with the best industry practise. It was important that staff in road vehicles as well as those at the trackside should be catered for. This meant deploying both mobiles (vehicle mounted sets) and hand portables. To be of maximum use, the radios should be capable of connecting to the BR telephone network but the Home Office was distinctly nervous about this and insisted that it must be only via a manual switchboard.

Thus a network of ‘radio areas’ was designed, each with its own control centre, connected to a number of base stations to give an estimated 95 per cent connectivity throughout the rail network.

Coverage

The propagation characteristics of Band II would allow coverage of between 20-30 miles from a hilltop base station, but railways seldom ran close to such places. Thus renting mast capacity from other site owners such as water towers, TV stations and others was an early decision. Contacts were established with these owners and site rental agreements put in place. BR radio engineers could legitimately work on the railway but be many miles from a railway line. This included some lovely parts of the country, like the Cat and Fiddle Inn, the second-highest pub in England!

How to prove the obtainable coverage needed some novel thinking and, in conjunction with BR Research, Test Coach IRIS was equipped with a radio signal strength measuring kit that would record radio signals as the train moved around. A boom aerial mounted out front simulated a person with a hand portable radio. In parallel, the BR radio team acquired a Land Rover and portable mast

together with a radio strength measuring van to assess coverage on the roads close to railway lines. Thus the network of both rented and railway-land sites was established. At the control centres, a geographic map was provided with the base stations marked on it such that the radio operator could relate a caller’s whereabouts to the correct base station.

Usage

From the outset, the radios were equipped with Selcall (Selective Calling) such that the operator would only call the person required. Inward calls would be by voice calling with the operator connecting to either another radio or to a telephone extension. Vehicle-mounted mobiles with their greater power performed the best. Hand portable coverage was patchy, with the helical aerial to accommodate the 105MHz frequency at a reasonable size not being particularly efficient. Later options of having a half wave dipole (about 50cm), but made of metal tapes that could be folded, gave better performance but were cumbersome.

Since the radio areas did not align with railway signalling or even control centre geography, the operating authorities decreed initially that the NRN could not be used for track to train communication, this latter being the role of the Cab Secure Radio system being developed in parallel.

By the mid 1970s, the network was in place, but use of the system was slow to take off. Some staff accepted the new facility with enthusiasm and useful improvements to faulting and maintenance resulted.

Updating technology and efficiency

The Band II arrangement was never very satisfactory and, in the early 1980s, the Home Office decreed that the Band would be closed down and replaced by Band III using frequencies in the 204MHz (base station transmit) and 196MHz (mobile transmit) Band. This meant re-engineering the base station network and providing additional transmitters to take account of the higher frequencies and known gaps in the existing coverage. BR was assigned 25 channels, greater than the previous allocation, with the promise of more if traffic levels demanded it.

Another annoying restraint was eliminated with the Home Office finally agreeing that automatic connection from the radio to the telephone network was permissible. This meant development of a new, much smaller, hand portable set which, with technology advances and the addition of a keypad, ultimately became the BRUNEL radio, introduced in 1991. Some wag decreed the name stood for British Rail Universal Network Electronic Link. The device was advanced for its time and enabled:

Network access to other radio control areas and the internal BR ETD (Extension Trunk Dialling) telephone system;

Point-to-point calls (individual and wide area);

Ability to prioritise communications;

Text communication;

Ability to transmit documents (although never invoked);

A network monitoring ability including call logging;

A single button for Emergency Calls;

Power adjustment to respond to incoming signal strength.

Similar features were built in to new vehicle-mounted mobiles.

The new sets were much more popular than their predecessors and, for a time, traffic levels increased. As well as allowing automated connectivity, a short code number was allocated to access electrification control rooms (ECRs) in an emergency to get the current switched off. By the mid 1990s however, the first public cellular networks were well established and there was a clamour from engineering staff that the smaller cellular sets would be better suited to the maintenance role. Thus the use of the BRUNEL declined even though the coverage at the trackside was often better than the public offerings.

Polmont and its aftermath

In 1984, an Edinburgh – Glasgow push-pull express with the locomotive at the rear hit a herd of cows at Polmont, resulting in the train being derailed at speed and 13 fatalities. The wreckage spread to the other track and, although no other train was involved, the potential seriousness of the accident led to demands that better communication to trains should be implemented. The Cab Secure Radio system was making slow progress and its relatively high cost meant it was only financed in areas where train crew savings could be made. Could the NRN be the solution?

By then, I was back at BRHQ as the Telecom Engineer so, after discussions with the radio team then headed by Les Giles, I was summoned to the BR Board to explain possibilities. Yes, we could offer something: it was not possible to route radio calls direct to the signallers as areas of coverage were incompatible; it would be possible to connect the radio centres to Regional Control Rooms by ‘hot line’ routing and then interconnect with individual signal boxes via the BR telephone network. It would also be necessary to improve coverage to around 98 per cent but stopping short of radiating cable in tunnels.

The necessary finance was quickly obtained and the radio team began to modify and enhance the infrastructure. In parallel, the traction and rolling stock engineers had to produce designs for equipping the multitude of locomotives and multiple units involving aerial fitment to roofs, robust power supplies and cab equipment consisting of mobile radio, microphone or handset, and loudspeaker.

The operators had little choice but to go along with this but tried to impose restrictions on usage – not to be used in place of SPTs, not to be used on the move. Very soon, however, as trains were equipped, usage found its own level. Drivers soon learned the telephone number of signal boxes and used the radio to report when stopped at a signal (what would you do if it was pouring with rain and you had the option of using a radio in the cab??). The train radios had an emergency button that would automatically connect to the Control Office if pushed. Signals in limited clearance areas were a safety risk and, after one driver was killed whilst using the SPT, even the operators sanctioned the use of the NRN. Such signals are shown with a cross on the diamond sign.

Accidents and NRN improvements

Accidents that do not happen do not make headline news but the NRN has prevented such occurrences on a number of occasions.

Regrettably, whilst the operators were getting used to NRN capability, at least one accident failed to be averted even though the radio had been used to report the initial problem. In 1995, a local Sprinter train on the Settle to Carlisle line was derailed by a landslide near Aisgill. Although a successful emergency call was made, this was to WCML Crewe Control. Responsibility for the Settle – Carlisle line had however been transferred to the North East Zone at York under Railtrack boundary changes but no account had been taken of NRN coverage areas.

Whilst the Crewe controller could have made a group call to all trains in the area, this was not done and instead the call was cleared and York control advised of the incident by telephone. In the ensuing mix up, a second sprinter train collided with the derailed train causing one fatality and several injuries. A six-minute window of opportunity had been lost.

From the ensuing enquiry, the Railtrack Zone Controls were better aligned to NRN areas and controllers were trained to react to NRN calls even if off their ‘home’ patch. A number of other improvements were made including dedicated emergency telephone numbers allocated to signal boxes, better recording and time stamping of radio messages, plus the need for controllers to regularly practise emergency scenarios.

These proved beneficial as, two years later, the NRN prevented what would have been a very serious accident. At Macclesfield, a points failure had caused a southbound train to cross to another line under verbal instruction from the signaller. A misunderstanding of the instruction by the driver led to the train proceeding northwards ‘wrong line’ to a ground frame location some miles away. The signaller noticed the situation whereby that train was running head on into the path of a southbound express. A quick call to Railtrack control resulted in an emergency call being broadcast which resulted in both trains being stopped within sight of each other.

Another example on the Settle – Carlisle line determined that a freight train derailment was caused by excessive speed by measuring the time between the train being logged as entering section and the emergency NRN call being received. Other examples of NRN emergency operational usage are known to have occurred.

The NRN system received a number of upgrades and enhancements which were engineered by the BR radio engineers and their successors and which included: base-station landline equalisation which dramatically improved performance, various software and configuration upgrades, antenna optimisation, additional radio sites to improve coverage, and uninterrupted power supplies for the 21 control centres.

So important did the radio become that trains were not permitted to enter service unless at least one on board radio was operative.

The advent of GSM-R and NRN’s replacement

The European development of GSM-R as the all-purpose radio system for railways has gradually led to its adoption in all of Europe including Britain. This has the capability of giving track-to-train voice communication, being a bearer for ETCS and communicating with engineering staff equipped with sets akin to the public cellular technology.

NSN’s Band III frequencies were also required to expand digital TV service, so the writing has been on the wall for the network for some time.

Working from the south coast northwards, the NRN service has been gradually replaced with GSM-R until, finally, an operating notice dated 12 Dec 2015 stated that the network would be closed on the 19 December.

That is not quite the end as the RETB systems on the Far North and West Highland lines in Scotland still use Band III frequencies but are being re-engineered into a different part of the Band, a project that will be completed in 2016.

So, farewell old friend, you served the railways of Britain well and it was a privilege to have been part of the team that enabled radio to become an accepted element of rail operation. Well done to the radio engineers within BR and its successors, and to the supply industry – initially Storno from Denmark and latterly Motorola – who developed the NRN system and its various radio products.

Thanks to my Rail Engineer colleague Paul Darlington who was also part of the NRN team and has added some of his memories to this article.