Ultra-fast rail concepts such as Hyperloop would have lower capacity than traditional high-speed rail and raise safety issues, according to an expert.
The concept of speeding along in vacuum-sealed tubes has captured the imagination since Elon Musk proposed that an ‘open source’ version of the technology be used to link San Francisco and Los Angeles.
A number of companies are vying to commercialise the idea, which was originally supposed to be a fraction of the cost of high-speed rail, with carriages travelling at speeds of up to 760mph in low-pressure tubes.
However according to Roger Goodall, an engineering professor at Loughborough University with expertise in railway propulsion and levitation, such a system has many drawbacks, including a potentially reduced capacity.
“I think the concept is intrinsically dependent on the vehicles being small, and the capacity is very much reduced compared with a normal long train with 10 or 12 coaches,” he told Professional Engineering. “If you compared a high-speed train at two-minute intervals with these capsules at 10-second intervals there’s a big difference in the number of passengers per hour.”
That’s simply because carriages travelling at higher speed need to be further apart for safety reasons. Safety is a major concern for Hyperloop that is often ignored among the hype, with extremely high potential forces when cornering or changing speed, not to mention if something went wrong.
“If you lost the vacuum, these vehicles would presumably suddenly stop very, very fast,” said Goodall. “In a tube that’s going to be horrendous.” He said the level of g-force would be equivalent to space flight or a military aircraft.
A recent twist on Hyperloop called Arrivo, set up by a former Hyperloop One engineer, suggests lower-speed, tunnel-free options for shorter journeys, with magnetic tracks running alongside motorways at up to 200mph. But Goodall said that cornering would still be an issue as motorways tend to curve more than high-speed rail lines.
There are other issues too, said Goodall, including switching tracks, and the problem of how you get this technology into city centres without an awkward out-of-town interchange.
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