Whilst I don't disagree in principle with HS2 there are a number of issue that concern me:
-First and foremost is the time scale. By the time the line is up and running will High speed rail still be the most effective technology available, or will new systems have been developed. (for example Maglev)
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-It has been said that trains will be able to run at 250mph using existing technology. Is this realistic, the fastest lines overseas currently run at 200mph.
Also trains will be able to run at approx. 3 min intervals again is this realistic.
These concerns contradict!
-Has the best route been chosen. The line won't connect directly to HS1 or Heathrow. Would a Frankfurt Airport style hub at Heathrow have been better and terminating the line at Stratford.
The line will connect to HS1, via an entirely segregated link. It is unlikely to be used much - at least during the day as Euston-St Pancras is not enough of a hardship and serving them such a pull on passenger numbers.
Stratford International is a white elephant and also unexpandable (especially not for turning 18tph around). Plus you would need to demolish a large area of Somers Town for Euston Cross (and given the long walks to the tube, it would be CR2 and Thameslink that will take all the strain, and despite the large trains and high frequencies they won't take it) as you would need a zone 1 station. If you plug HS1 and HS2 together, then the cramptness and passenger congestion (roughly 300 passengers a second boarding trains to the north and the same disembarking from the north) will increase as you get the HS1 passengers as well, only losing a handful of passengers for through journeys. All in all an unpleasant experience for the sake of a tiny fraction of passengers (perhaps those who live west of Euston are somehow more important than those east of Euston - similar area demolished in both cases).
-Will the line at Birmingham be a terminus. Does this mean services beyond will have to reverse back out or will they by-pass Birmingham.
Yes and the latter.
The spur will allow access to all three Birmingham radials (London, NE, NW), while the two northern routes will have access to the London one avoiding a reverse and can stop at Birmingham International en-route.
This all saves a massively expensive through-Birmingham route that wouldn't be sensible or direct for the NE.