Just to check I'm understanding this right; you want a 158 allocated to Wick to provide a "shuttle" connection into the Thurso - Inverness service?
A fifteen mile trip to Georgemas/ Halkirk four times a day (i.e. the frequency of the Thurso - Inverness train)?
The Wick that gets around twenty five departing passengers per day, on average? (17,890 passengers in total - half of whom are arriving, half of whom are departing - divided by the number of days in the year...)
Sort of.
Any additional units would be allocated to Inverness. The shuttle would require one unit, but it would not be the same unit. Maintainence requirements etc. mean it would need to go to Inverness, thus 158s would interwork between the Caithness shuttle and the Thurso to Inverness services. Part of the timetable overhaul may mean that the crew depot is moved to Thurso from Wick. Whatever happens, there will only be one crew depot (and therefore one stabling point) in Caithness. Whether it is Thurso or Wick is immaterial. Thus, the units that are already stabled up north overnight can be shuffled as required for the next day's service.
The additional Caithness unit would provide two roles:
1: Shuttles between Halkirk and Wick to connect with the Thurso to Inverness service.
2: Services from Wick to Halkirk to Thurso, providing additional services between those three towns in the times where the unit would otherwise be sitting idle.
This shuttle is, as I state again, a compromise between the current system (where services to Wick must travel via Thurso, thus adding 30 minutes to the journey time) and the previous system (where trains ran as 4 coach services, dividing at Georgemas).
I have already briefly addressed the statistical point. I'll expand:
The reason patronage on the northern section Far North Line is stagnant (and for the case of Wick, declining) is because the service level has remained stagnant, and has been very unreliable in the past few years. When the service was previously increased, more passengers used the train. Therefore, if new services are increased, more people will use the train.
Secondly, the line takes a lot longer than the road. For Wick, this is compounded by the detour to Thurso. Thus, any significant decrease in journey time (30 minutes is significant) will encourage passengers back to the train who have previously abandoned it, and also new ones.
The ~17k figure you quote for Wick is the lowest recorded (I can only see back as far as '02/'03) bar the period '06/'07 because of these reasons. The highest it has been is 25,666 ('10/'11).
