Now we are getting somewhere, I wondered when this would be suggested. This is the proposal that I have made reference to already.
So, pick...sorry, scrutinize a joined up proposal to have a cross rail type service between Banchory and Peterhead Fraserburgh.
F&B would be on new alignments north of Ellon, per thread already referenced and would start initially at Banchory.
There's nothing actually stopping you from reinstating it on the old trackbed, except longer journey time to Peterhead and the displacement of pedestrians/cyclists between Dyce and Maud (should be single north/east of Maud anyway with room for a path at the side).
Not a bad idea, 2tph Montrose to Fraserburgh/Peterhead, stopping at :Laurencekirk, Stonehaven, Porthlethen, Cove Bay, Aberdeen (Central), Kittybrewster (for Aberdeen Uni), Dyce, Newmachar, Ellon, Maud, then Mintlaw to Peterhead or Strichen to Fraserburgh (2tph to Maud, 1tph to each terminus).
Then 2tph from Inverurie to Banchory, stopping at: Kintore, Dyce, Kittybrewster, Aberdeen, Ruthrieston, Cults, Milltimber Parkway, Peterculter, Drumoak and Banchory. Add peak extras and you have an attractive service there.
You could run the Aberdeen to Edinburgh/Glasgow/Inverness and vice versa fast to Stonehaven/Inverurie respectively to speed up journey times for those passengers, now these services are available.
Apart from the cost of rebuilding the Banchory line/ F and B and redoubling between Dyce and Aberdeen, the cost of the project is relatively affordable.
17 miles to Banchory + 57 miles to Peterhead is 74 miles. 74 * 20 (lower end of Bald Rick's estimations, given the mostly or entirely preserved trackbed on both lines) is 1.48 billion. Try the upper end of his estimate and it turns out as 2.2 billion.
As for Dyce to Aberdeen, the tunnels add complication, however the North Cotswold Redoubling project in South East England cost 67 million in 2009 for 20 million. Inflation using the Bank of England's calculator would make that approx 91 million (/ 20 = 4.5 million). Allowing for resignalling and tunnel complication, a conservative estimate would be 15 million.
Additionally, it may be sensible to redouble the remaining part of Aberdeen to Inverness to allow those trains skipping stops to Inverurie to lower the overall journey time to an hour and a half.
Using that Cotswold estimate , updated to 2021 figures, it would cost approx 400 million for roughly 88 miles of redoubling (91 million * 4.4 = 400.4 million (20 miles * 4.4 = 88 miles).
400.4 million + 15 million ( for redoubling Aberdeen to Dyce) + 1.48 to 2.2 billion = approx 1.9 to 2.61 billion.
Given TS are spending 3 billion on upgrading only 6 more miles of A9 to dual carriageway in another region, it's certainly a decent proposal to adopt and campaign for. In the current climate, it could be the environmentally-friendly alternative to dualling from Nairn to Inverness, to build this project and redouble the remaining single part of Aberdeen to Inverness at the same time, cutting journey times to an hour and a half between the 2 cities(much quicker than driving) as a 1.9 to 2.61 bn project (at least 390 million cheaper than the proposed A96 dualling from Nairn to Inverurie alone) in total.
The Greens would greatly prefer the railway redoubling to the A96 and they may still be supporting a minority SNP government, depending on how this year's Scottish Parliament election goes for the SNP.