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SIGNALLING/TELECOMS
CLIVE KESSELL
Combatting SIGNALLING FAILURES S
ignalling failures have always had the ability to cause delay to train services and, whilst modern signalling technology is designed to be more reliable, when failures do occur they can be much more significant as the systems are complex, often involving software as well as hardware components.
The results from the latter were deemed successful and Network Rail is proceeding with an operational trial between Castle Cary and Westbury on the West of England main line. Chris Fulford, who has been the lead engineer on the project for some time, gave a report of progress to the IRSE London & SE section recently and has since given more details to Rail Engineer.
Problems to be overcome
In such circumstances, the local technicians can struggle to understand the nature of the fault and to apply the right diagnostics. Technical support from specialists, often the original suppliers, has to be brought in to assist. A recent failure of the Ansaldo system between Cheadle Hulme and Crewe lasted for three days, with the line being closed for that period. Network Rail was left with a large bill in compensation for the delay to trains. And, of course, passengers were badly inconvenienced, which didn’t help the ‘Putting Passengers First’ programme.
Rail Engineer | Issue 186 | September/October 2020
Rail Engineer has been following the progress of a system intended to minimise the effects of such failures and three previous articles have been published. Firstly in issue 129 (July 2015) when the project was known as COMPASS – Combined Positioning Alternative Signalling System, secondly in issue 155 (September 2017) when a new name – Degraded Mode Working System (DMWS) was introduced – and thirdly in issue 162 (April 2018), describing the results from a conceptual demonstration being tested on the Hertford Loop test track.
Signalling failures take many forms – loss of the signalling power supply, cable theft or damage, track circuit or axle counter failure, loss of communication between the interlocking and external equipment, component failures, control panel failures, plus several others. Some recent improvements to signalling reliability have already been made – the use of intelligent infrastructure, more resilient power supplies and better cable management. However, failures still occur, and it can take a long time to set up current degraded mode working methods, now generally known as Emergency Special Working. The aim of DMWS is to reduce this time of, typically, three hours to 15-20 minutes.
