Earlier you said 4/5s was up for grabs, and now you are saying it will get 50%. Where are you getting that figure from?
The three main factors in people decision making are likely to be cost, time, and convenience. Given that we have no idea what the cost will be, and convenience is difficult to measure (at least without really detailed studies) your argument appears to largely be based around the time saving. Please accept my apologies if this isn’t the case. But given this you appear to be saying saying that a saving of 48 minutes (Edinburgh) and 50 minutes (Glasgow) is enough to convince 50% of the entire air market to shift. Given what we know about the market, with 25% being transit passengers, and it being split across five major airports covering pretty much the whole of the SE and some of the south midlands, I’m deeply sceptical about this. Maybe 50% of the non-transit passengers. At a push.
Now if you were talking about a high speed line all the way to the central belt I’d be very much inclined to agree, because it would save another hour, increasing the influence of Euston/OCC on folks decision making. But at the moment it’s only going as far as Wigan, and unfortunately, it might not even get that far.
I’m really not helping myself here, by not making things clear.
The premise of this entire thread (since I joined it about halfway through) was that a high speed line all (or at least most of) the way from the end of HS2 at Golborne to Scotland could be justified by capturing London - Scotland air traffic. I disagree with this premise.
I do agree entirely about the cost / journey time / convenience equation, which is something I have banged on about for years when writing on these pages in discussions about mode share / switching. Probably too often.
Specifically about this discussion:
1) rail already has around 25-30% of the London - Central belt air/rail market, with journey times of c4h30
2) HS2 2b will knock almost an hour off those journey times (22%), and increase frequencies, making it more attractive. This will capture around half* the current air traffic, including a small but not insignificant proportion of transfer traffic at Heathrow. To make the maths easy, let’s say it moves rail/air market share from 25/75 to 60/40.
3) of the remaining 40% flying, somewhere between one third and one half (15-20% of the 40%) will be transfer passengers at Lonodn airports, principally Heathrow, and most will not swap to rail even with further journey time improvements.
4) that leaves around, say, 20-25% of the existing air/rail London - Central belt market who will still be flying post HS2 2b, but not transferring at a Lonon airport, ie around 2m passengers.
5) spending double digit billions on further high speed line construction through the north of England and Scotland is a big price to pay to win 2m passengers a year. The journey time benefits accruing to the rail passengers already on the services post HS2 2b are also unlikely to justify it.
* the ‘half of existing passengers’ is consistent with the results of other high speed rail projects with similar journey times. It is also supported by modelling, including some I did a long time ago. It could, of course, be wrong. Perhaps most relative is that knocking 40 minutes off London - Manchester rail journey times (25%), and trebling frequency, reduced flights MAN - London airports from 40 rotations and 2m pax pa in 2005 to 8 rotations and half a million pax today. Other posters have quite rightly pointed out that the improved rail service wasn’t the only reason for this change, but it was a very significant factor.
A final point, just checking my notes from 2005; there were more air passengers from London - Central belt back then than there are now, c6.2m then vs 5.8m now. Interestingly the fall has been almost entirely from Glasgow, whereas Edinburgh is much the same. Rotations from Glasgow have reduced from 44 daily to 30, whilst Edinburgh is broadly the same. And of course, in that time, rail journey time to Glasgow has fallen by about 40-50 minutes (14%), and frequency doubled, whereas to Edinburgh journey times are roughly the same, and frequencies have increased, albeit mostly at off peak times. On top of it all, the market has grown, and all the growth has come to rail.