What do you take 'socio-economic reality' to mean, exactly, in this context?
What I mean is:
1) The marginal cost of running a sleeper train to the far north from the central belt would be significant. At least £4m a year, probably more.
2) the number of people who want to travel from Inverness and south thereof to the far north is, frankly, small. Rather less than 200,000 single rail trips pa north of Dingwall, and only around half of those are north of Tain. This includes all trips ‘internal’ to the FNL.
3) Kirkwall airport handles around 150,000 people a year to and from the central belt, Inverness and Aberdeen, of which well over a third are to/from Aberdeen.
4) The Scrabster ferry carries about 150,000 passengers a year, which includes all those in cars and coaches. It’s reasonable to assume that a significant majority are in cars or coaches, and a good proportion of them are to and from Caithness rather than further south.
5) even if we pretend that all of the ferry passengers, and all of the rail passengers, are in the same market as the potential sleeper, it’s a total of around 400,000 single trips a year. Let’s be honest, it’s going to be rather less than half that that are travelling to Inverness and south thereof. But let’s say 200,000, being very optimistic.
6) the London to Scotland market has around 11 million passengers a year travelling by air and rail alone. Caledonian Sleeper has a little less than 2 % of the market.
7) continuing with the optimistic mood, with a following wind, and rose tinted spectacles, let’s assume that a Far North Sleeper could capture more than double this share, ie 4% of the market. That would be 8,000 a year (about 12 each way per train). A cost of £500 each, at best.
8) even if every passenger was willing to pay double the standard single price of the full distance from Glasgow to Wick (£71), regardless of their journey, it would need a subsidy of £350+ per single trip.
9) this compares to a single trip bus cost of £21.60 from Wick to Inverness, and typical air fares of around £120 from Kirkwall to Inverness, or £200 from Kirkwall or Wick to the central Belt. These are operated on commercial terms.
So, on a whole set of (very) optimistic assumptions, we can see that such a service would require a very significant subsidy, with alternatives that are far cheaper, and generally quicker.
If the assumptions were set more realistically (smaller market, similar 2% share for sleeper) it is likely that the subsidy per passenger would be well north of £1000. And then we are in the territory of offering chauffeur driven Range Rovers as a more cost effective alternative. Hell, even private helicopters.
That is socio-economic reality.