It's just so, so much nicer to head up via Altnaharra, Strathnaver and the coast road.
Some would say there is nothing to see going that way, just hills and heather, but it makes a change for people not used to hills and heather
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I would not consider using the Inverness to Tain section of the A9 as I simply find it unpleasant due to motorised traffic. There are one metre strips on parts of the route which make it feel safer, but not throughout, however there are viable alternatives.
North of Tain the motor traffic thins out a bit, but it's difficult to advise others if it thins out sufficiently
. I prefer the coast road myself because it passes though communities where you can take a break and have a look around.