Vacuum trains: a high-speed pipe dream? (BBC Future)

[caraher]

18. These are not dealbreakers

You just need more sophisticated air handling than airliners use. We keep people in space for months on end; air quality is a minor technical issue. Depending on the use of the tunnel and pumping speed one could even imagine venting gases out the rear if there were a need to do so.

Concerning acceleration, why assume unbelted passengers? On an airliner you are belted for substantial periods of time that do not exceed those required for accelerating and decelerating one of these trains. Airliners might be a good benchmark for realistic readily-tolerated accelerations - they're well short of 1 g, but I'd say closer to 1/4 than 1/10 of a g.

I'm not obsessed with the hypervelocity claims and 1-hour travel times; I do think there could be substantial benefits to this approach for shorter trips and slower speeds.