HS2 at risk of derailing at top speeds, report finds
Secret research for the rail project warns of catastropic track failure without costly alterations
By Andrew Gilligan
Trains on Britain’s HS2 rail scheme are at risk of derailment and catastrophic track failure, according to previously secret research commissioned by HS2 itself.
Engineering changes will be needed to make the project safe, the study says. The alterations will raise costs, increase journey times, or both, and will “collapse” the scheme’s already shaky business case, according to opponents.
Ministers claim that HS2, running between London, Birmingham, Leeds and Manchester, will revolutionise rail travel and shrink the North-South divide.
But the findings today revealed by the Telegraph will reignite debate over whether the project, already costed at £50 billion, is a good use of public money.
In the research, completed last year, Prof Peter Woodward, one of the world’s leading experts in the geo-engineering of railways, found that the speeds proposed by HS2 – faster than any other high-speed line in the world – would create “critical track velocity effects” and “significant issues” with track instability.
Prof Woodward said that the ballasted track of the kind to be used by HS2 “may not be able to adequately retain the track geometry” at the 225mph line speed proposed. He said that “embankment instability, particularly over poor soils … will generate significant issues during construction and operational running”. Around 107 miles of the route, about a third of the total length, will run on embankments.
The research, classified “official-sensitive”, was commissioned after Prof Woodward warned that high-speed running created track problems that “may threaten the stability and safety of the train”.
He said that speeds as high as those planned by HS2 could cause “rapid deterioration of the track, ballast and sub-ballast, including possible derailment and ground failure”.
On Saturday, HS2 officials welcomed the analysis and said that detailed designs would be drawn up as they examine the ground along the route.
However, they declined to comment on the implications for the scheme of having to reduce train speeds, or say how much more money might need to be spent.
HS2 plans to start operations with trains running at 225mph in routine service, then increase speeds – to 250mph – within a few years. Most high-speed lines, including Britain’s Eurostar, run no faster than 186mph in routine service and the world’s current fastest rail-based trains, France’s TGV Est, travel no faster than 200mph.
Research by David Connolly, a colleague of Prof Woodward’s at Edinburgh’s Heriot-Watt University, has found that the safe maximum speed on the soft soil that occurs along much of HS2 may be as low as 157mph.
To avoid the danger, HS2 may have to be slowed to that speed on severalstretches, cutting or even eliminating its advantage over conventional rail. Alternatively, there may need to be massive works to stiffen the ground the line runs over, potentially adding billions of pounds to its cost.
Another expert in the field, Prof Victor Krylov of Loughborough University, who produced an influential early academic paper on the subject, said the danger was of a “ground-vibration boom, similar to a sonic boom”, which causes a sudden and “very large” increase in generated ground vibrations.
“What matters is when you cross the [speed] barrier,” he said. “If you do that, ground vibrations can increase twenty, thirty times.”
Prof Krylov said the effect, known as a “Rayleigh wave,” was greatest in soft ground and had been observed in trains travelling as slowly as 110mph in Sweden, across alluvial soil.
“The most straightforward way to improve the situation is just to make the ground stiffer – by injection of concrete, or by piling,” he said. “But the best or cheapest measure you can do is just to reduce the speed.”
However, HS2 needs to run at 225mph if it is to meet its ambitious business case and capacity claims.
Its planned two-track core route between London and the Midlands is supposed to be able to handle the traffic currently served by three separate main lines, to destinations including Birmingham, Manchester, the East Midlands, Sheffield, Leeds and Scotland.
HS2 claims it will be able to run up to 18 trains an hour – one every three minutes 20 seconds – along the core route, more than on any other such high-speed line in the world.
If the trains had to be slower, frequencies would have to be reduced, putting at risk the promised service to many destinations.
Running at the industry standard of 186mph would cut the scheme’s already shrinking benefit-cost ratio by 15 per cent and erode the advantage over conventional rail on the London- Birmingham journey to only around 15 minutes. Running at 157mph would make the journey on HS2 only a few minutes quicker than the current conventional line.
The disclosures are the latest blow to the scheme, viewed by many even in the rail industry as unnecessary.
Last week, it emerged that the National Audit Office, which has been fiercely critical of HS2, was to begin a third review of the project. It also appears likely that the approving legislation will not now clear Parliament this year, amid anticipated delays in the Lords.
Based on months of computer modelling and work on testing rigs, Prof Woodward said his simulations “clearly show the development of Rayleigh wave effects… [and] the development of critical track velocity effects.”
He recommended massive ground stiffening and said that the track should be laid on a concrete slab. However, this would be more expensive and much noisier than ballast.
A spokesman for HS2, Ben Ruse, said: “We support the work by Prof Woodward. We recognise the need to mitigate for the phenomenon of Rayleigh waves and we have done. The detailed design will be based on the specific ground investigation works we are undertaking as we get access to all the route.”
HS2 declined to comment on the implications for the scheme of slowing down trains, stiffening the ground or switching to slab track.
