Rats cause near disaster on a railway by chewing through signal cables

In a new press release, the British Approvals Service for Cables (BASEC) says that in the beginning of July, a high-speed TGV train was struck from behind by a regional train in south west France. The regional train had passed a signal wrongly set on green at 120 km/hr and moments later it ploughed into a high-speed TGV train that had 178 aboard as it travelled to Paris. Miraculously only three people, of the 40 injured, were seriously hurt. No one was killed.

 

This potentially catastrophic malfunction was caused by rodents gnawing through trackside signal cables, an SNCF inquiry found.

 

The accident at Pau has prompted the French national railway to carry out an urgent check on 10,000 signals to prevent what it says was an incident that was ‘exceptional and unprecedented’.

 

However, a quick trawl through Google shows that such experiences are far from ‘exceptional and unprecedented’. Such incidents are certainly not  totally freak. To take just one of many other recent examples, in Australia, delays continued on four train lines as metro staff scrambled to fix damage from a fire likely caused by rats. Passengers experienced delays up to 20 minutes, more than 24 hours after a fire sparked commuter chaos. Rail workers said that the fire near Richmond railway station, Victoria, was probably caused by rats chewing through 12-year-old heavy-duty cabling covers and exposing high-voltage cables.

 

In the UK, a small hole gnawed through an inch-thick high voltage power cable caused a breakdown on the West Coast mainline in Cheshire. This led to 20 train cancellations and 99 delays. And just a couple of weeks earlier, a special service carrying football fans to a Carlisle United match against Everton was one of 107 trains cancelled (and another 289 delayed) by a similar problem between Preston and Lancaster.

 

So this is a common and serious problem that occurs throughout the UK, often with the risk of potential disaster, and rail chiefs know that they need to spend millions to prevent rodents from doing this kind of damage to signaling, power and telecommunications cables laid alongside the UK's 20,000 miles of rail track.

 

Cables gnawed through by vermin can result in electrical short circuits and fires and, as in the case of the Pau train collision are significant threats to life and safety. Network Rail has already started a two-year programme to strengthen the rail system's resistance to such attacks by laying steel armoured replacement cables.

 

 

Dr Jeremy Hodge, chief executive of BASEC, says the threat from rodents and others to cabling and the systems they carry is always with us and presents serious challenges to specifiers, installers and end-users.

 

He commented: “We receive many enquiries about how to protect cables against rats, mice, squirrels, pigeons and even insects – with the first three the most pernicious and determined.

 

“They can gnaw at cables to create nesting material. Rats must gnaw as their teeth grow constantly and it does not help that a rat’s tooth is harder than iron. Cables under floorboards, in outbuildings and in ducts are commonly affected, including power, data, final circuit installations and fibre cables. The wiring looms of motor vehicles are also regularly attacked.”

 

 

BASEC points out that the IET Wiring Regulations (BS 7671) set specific requirements for designers and contractors to assess ‘External Influences’ such as fauna (coded as AL), in Section 522.10.  The normal condition (AL1) is with no vermin present. 

 

Where ‘aggressive fauna’ are experienced or expected (AL2), an appropriate choice of wiring system or special protective measures must be used such as cable with better mechanical protection, by using more appropriate routing or locations for the cables, or by providing additional protection such as conduit.

 

 

Jeremy Hodge says that preventing vermin damage has three lines of defence. The first is building in physical barriers or deterrence including routing cable to avoid spaces where rodents live or travel such as under floors, or embedding in conduit, plaster, cement or concrete.

 

Selecting the most suitable cabling for use where vermin might be present is recommended. Regular cable such as PVC conduit wire or flat twin and earth offers no protection against gnawing, but steel wire armoured or steel braided cable offers some protection, though the sheathing itself may be attacked. Mineral insulated cable or steel conduit offer good protection.

 

“It is possible”, he says, “to include bad tasting deterrent additives into the sheathing material of some cables, but these have limited effect with mice or rats and they are mainly used overseas where damage from insects including termites is a significant problem.”

 

 

Taking care of the pests themselves is, says Jeremy Hodge, “an effective way to prevent or reduce further problems.” He says that advice should be sought from specialist firms, but less costly is to ensure that holes, cavities and voids – even the smallest, are blocked up in buildings and that any source of food from waste and litter is removed.

 

It is, he concludes, unlikely we are going to declare victory over rats, mice and squirrels soon, but by remaining vigilant and adopting sensible preventive measures, we can help guard our vital systems and infrastructure against their attacks.

 

Further information about BASEC is available at www.basec.org.uk or you can contact BASEC directly at [email protected] or +44 1908 267300.