50216 Right side failure on automatic warning system at SN74

August 2011 in Network Rail and Suppliers

Signalling South West

A reporter is concerned that there is a right side failure occurring on the Automatic Warning System (AWS) magnet at signal SN74, located on the Down Main Line at Thingley Junction.

A right side failure means that Drivers receive a horn in their cab instead of a bell when they approach a green light at signal SN74.  The reporter is concerned that because this has been ongoing since the beginning of June, Drivers may become accustomed to cancelling the horn when the signal is green.  Through habit this could eventually result in a Driver cancelling a horn assuming the signal is green, when in fact it is a single yellow. This could lead to a Signal Passed at Danger (SPAD) if the following signal is red.

 A notice has been displayed on the late notice board that informs the Drivers that"the problem is due to a cable fault on signal SN74.  Drivers will receive a code 2 AWS fault.  Network Rail is aware of the fault but at present there is no estimated time for rectification".

The reporter does not feel that this satisfactory and believes that the problem should be rectified within a certain timeframe.

 Could Network Rail:

• Provide details on whether there are any fixed timescales to rectify faults such as these?
• Clarify how long it will take to rectify this fault with the AWS magnet at signal SN74?
• Ensure that this fault is rectified as soon as possible to reduce a SPAD risk

Response from Network Rail

Network Rail would like to thank the reporter for bringing their concerns to our attention.

Could Network Rail provide details on whether there are any fixed timescales to rectify faults such as these?

All faults are repaired where possible by the attending fault team when reported. Where this is not possible due to, for example, the size of the repair/available track access, rectification is prioritised with guidance fromStandard NR/L2/SIG/19807 'Prioritisation of signal engineering equipment defects'.

Faults of this nature, along with all signalling failures, are treated very seriously. Each failure is normally attended to within one hour and any further work required is either carried out there and then, to bring signalling back to normal, or is prioritised along with all other failures. If immediate rectification cannot be carried out then the signalling system is always left in a safe state. A discussion will always take place between the maintenance and the operations teams to decide the most suitable method of signalling trains during a degraded mode such as with this case SN74.

Could Network Rail clarify how long it will take to rectify this fault with the AWS magnet at signal SN74?

There have been two key faults with this AWS equipment during the past six months; the first being a defective electro-magnet and the second a faulty lineside cable. The first failure took longer than expected to repair due to seized bolts on the securing plate which prolonged the access and equipment needed to bring about a fix. This was achieved on 5 May 2011.The second failure required a new 200 yard section of cable which had been failing intermittently. This work was carried out on 5 August 2011.

Could Network Rail make sure that this fault is rectified as soon as possible to reduce a SPAD risk?

The fault with SN74 AWS was rectified on 5 August 2011 by renewing the cable.​