I didn't realise how ambitious HS2 is:
If you stood by the track, a train could pass you at 360km/h (224mph) every 3 1/2 minutes - the kind of safety and control systems to make that possible must be astounding.
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> the kind of safety and control systems to make that possible must be astounding.
I wondered about this, and hit gold on Google: the requirements specification! https://assets.publishing.service.gov.uk/government/uploads/...
HS2 will, unlike the rest of the UK legacy network, use ETCS: https://en.wikipedia.org/wiki/European_Train_Control_System (at level 2 with the possibility of level 3). Conceptually it's the same as the ancient tokening system - a train requires a token to enter a particular section of rail. Except these are digital tokens granted over a cryptographic protocol over the GSM network or trackside radios. When a train has cleared a particular point, a calculation is made based on the speed and braking distance of the train behind, which is then granted an authority to move further along the track. As long as the train receives a continuous series of valid "movement authority" tokens for the correct sections, it will proceed. If not, it applies the brakes.
(That's a really nicely written requirements document - concise, but including rationales for every point. More reading on the crypto: https://www.cs.bham.ac.uk/~tpc/Papers/TRAKS.pdf )
> GSM is no longer being developed outside of GSM-R, the manufacturers have committed to supplying GSM-R till at least 2030. The ERA is considering what action is needed to smoothly transition to a successor system such as GPRS or Edge.
While I’m always happy to keep using something that works, « upgrading to EDGE by 2030 » still gives me a laugh.