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Although the number of potentially high-risk train accidents (PHRTAs) has increased in the last three years, according to data released by the Office of Rail and Road just days before the incident, the numbers are decreasing over a longer trendline. And of the 23 PHRTAs last year, only five were derailments, two of which involved passengers.
“We should not forget that rail is a very safe form of transport in comparison with most other modes, especially private cars,” says William Powrie, professor of geotechnical engineering at the University of Southampton.
Still, five derailments is more than none, and the rail industry and its engineers want to prevent all incidents. “It does need acting upon,” says Paul Allen, assistant director of the Institute of Railway Research at the University of Huddersfield. “If people had died as a consequence of that train fouling the adjacent running line, it might be a slightly different conversation.”
It is broadly accepted that the likelihood of this type of derailment is going up because of climate change-related weather making embankments unstable, Allen says. One solution to that issue, he continues, is to “identify high-risk locations across the network and put mitigation in place at those specific locations”. Doing so is the most cost-effective way of reducing the overall risk of a derailment due to a landslip, he says.
“We’re not going to be able to stop landslips,” Allen continues, so mitigation is important. That can include better preparation of the area around tracks that are prone to landslips to stop anything getting on the track.
“Derailment prevention guards alongside the running rails on the track, and also guides on the bogies to prevent excessive lateral movement on the train” are two technologies that the UK could deploy more frequently, Powrie says, learning from Japan. Other systems that could be adopted include fibreoptic early warning systems, which send automatic alerts if objects or mud falls on to the rails.
A similar technology is already in use on parts of the UK rail network, says Nick Koiza of Smart Component Technologies, which deploys sensors on the bearer and sleeper next to the rail.
“Every time a train goes over that particular area of track, what we do is we take measurements that provide an indication of the extent to which the track is moving,” he explains.
The scale of the movement allows Koiza’s system to determine when things need to be assessed by humans, freeing up time and staying more proactive across the whole network. “What we’re doing is we’re replacing some of the on-track workers with these devices that are the ‘eyes’ on the track.”
The key question is the extent to which those in authority believe action is needed, versus the outlay of doing so. “It would come down to a balance of cost and risk,” says Powrie. “Derailments on the UK network are fortunately rare, and as we saw [this week] and in earlier incidents such as the Lambrigg West Coast derailment, the crashworthiness of modern trains is excellent.”
It’s for that reason he believes more work should be done on trains than on the tracks themselves. “Infrastructure modifications are expensive if applied over many kilometres, hence it is usually better to make improvements on the vehicles,” he says.
Powrie points out that British trains have already made major strides in crashworthiness in the last half-century, moving away from the slam-door stock. More targeted interventions where incidents have occurred – and are likely to occur – are the best way to spend while staying safe, he reckons. “We learn from these incidents and design new infrastructure and vehicles to be safer – but blanket, network-wide retrofit is often not feasible.”
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