Third-rail safety

Among the letters expressing support for third-rail electrification (Open Access, RAIL 962) was one asserting that it was unsafe.

For note, EC4T (Electric Current for Traction) does not feature in the risks listed in the Office of Rail and Road’s annual report.

A couple of years ago (prior to COVID), I was curious about

how unsafe third rail EC4T was, both in itself and compared with 25kV overhead, because the public reaction on safety is qualitative and often fact-free.

By means of a Freedom of Information request to ORR and an internet search of newspaper reports (bad news is good press, so most incidents get publicly recorded), I compiled a list of electric shock events involving EC4T over the years 2014-19, quantified in FWI (Fatalities and Weighted Injuries).

For explanation, FWI is a statistical tool, used for example in cost:benefit analyses of improvement works at road accident blackspots. A death is counted as 1FWI, a serious injury as 0.1 FWI, and minor injury as 0.01 FWI, hence the ‘Weighting’ term.

My analysis showed that, averaged across the electrified network, per year EC4T was responsible for 0.47FWI/1,000stkm (FWI/thousand single-track kilometres) in third rail areas, and

0.23 FWI/1,000stkm in 25kV territory.

The Department for Transport monetises 1FWI at £1.6 million (2016 figure) for cost:benefit analyses. Also, there is a convention that in an ALARP (As Low As Reasonably Practicable) harm-reduction argument, it is unreasonable to spend more than three times the cost of the harm to prevent that harm.

This means that it is worth spending £5m per FWI annually on any effective safety-related scheme. For third rail, this works out to £2,350 per stkm, or £28,000 as a capital spend discounted over 20 years.

This is not a very significant sum - enough for platform end barriers or additional fencing at vulnerable access points to deter trespass onto tracks, but not enough for technical measures such as

energising only when a train is in section.

It certainly does not justify blackballing any third-rail electrification proposal on safety grounds.

Robert Graham Blakey, Somerset