Rail Engineer • March 2016
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Test coach IRIS at Wlton Junction, Kirkby, in September 1991.
SIGNALLING AND TELECOMS
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 reengineered 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.