When on a motor caravan holiday in the mid/late 1960s, I can recall seeing somewhere in the Ballachulish area proposals (for consultation?) for a road to connect Rannoch Stn to the A82. Looks like nothing became of it.
That was part of a proposed E-W link from the A82 over Rannoch Moor via Rannoch Station and from the A9 through the Cairngorms via the Lairig Ghru connecting from just North of Kincraig near Kinrara past Loch an Eilein to the footpath fork known as Piccadilly and on into the Lairig Ghru.
I've heard about this from people of various generations with connections to the Scottish mountaineering and ski communities and people with a lot of knowledge about the Cairngorms, but never found any maps or official info on proposed schemes cropping up online. I've heard mention that a monorail was even proposed from Braemar to Aviemore in the 1960s!. Perhaps they were akin to the modern day DMRB stage 1 sifting process routes for the A9 and A96 dualling such as taking the A9 over the Corrieyairack Pass and through Whitebridge and Farr to Daviot or re-routing the principle Aberdeen - Inverness Trunk Road via dualling of the A939 Lecht Pass!
If the Highland population hadn't fallen by over half since the formation of the UK in 1707, a time period in which the UK's population increased 10 fold, many of these hypothetical routes would have naturally evolved from historic drovers routes to modern communications. Far from being natural wilderness that has 'quite enough people driving all over sensitive parts of Scottish landscape as it is', far too much of Highland Scotland is more accurately described as a human wasteland, unnaturally emptied of it's townships and people. Far from improving the ecological condition, far to much of upland rural Scotland is now ecologically in a worse condition than when far more populated under a more diverse and sustainable land use pattern. Whether by overgrazing by an unsustainable number of red deer and/or the over dominance of a monoculture of excessively managed grouse moors, far to much is now in the unfortunate category of being both an ecological and human desert.
Which if any of the proposals such those around in the 60s would be acceptable in ecological terms given the current history of the Highlands is a long debate, an E-W connection across Rannoch Moor would reduce the sense of remoteness, but it is already crossed by a railway and a major arterial trunk road and human perception of wilderness and remoteness does not necessarily correlate with actual environmental impact. The impact on the scale of the moor would be slight, where as the impact of a road to the scale of the Lairig Ghru would be huge (and a road on Rannoch Moor is far more practicable in terms of winter operations than one through the Lairig Ghru).
I suppose an interesting aspect related to this discussion is what historic or completely new routes would you like to see today? If I could have one piece of old infrastructure, it would be the railway up the Great Glen, but extended to Inverness. I recall seeing some discussion here about a rail link from Tulloch to the Highland Main Line, I certainly think it is a loss to the Highlands that there isn't a within Highland rail link from Fort William to Inverness given FW being the second largest population centre within the Highland Council area. But I guess such a link if built would pose a threat to the WHL between Crianlarich and Tulloch over Rannoch Moor?
The OP in this thread was really about the issue of East-West links in Highland Scotland and they generally aren't good, so for a new piece of infrastructure I'd punt in relation to the A9 dualling, a new A86 alignment from near Ralia, Glen Truim to the existing A86/A889 junction, giving a shorter and vastly better aligned route and taking E-W traffic out of Dalwhinne, Newtonmore and Kingussie respectively.
