The A821 is either a 'tourist route' or a heavingly stomach-churningly twisty drive, depending on the nature of your journey. It is undoubtedly a very scenic drive, and one which is very definitely slower than the alternative A81 route, despite only being a couple of miles further.
Braeval - Kilmahog
The A821 begins about 2 miles south-east of Aberfoyle on the A81 Callander Road, and also ultimately ends up near Callander, but takes very much the long way round. Passing through the tourist den of Aberfoyle there is no hint of what's to follow, but at a former TOTSO with the B829, the route swings sharply right and climbs a series of hairpin bends up into the foothills of the Trossachs, and so we're off! The Forestry Commission's David Marshall Lodge nearby marks the remnant of the Queen Elizabeth Forest Park (most of it was swallowed up in the Loch Lomond and Trossachs National Park), and is home to a variety of walks and activities. From here the road winds, swerves and generally heads in every possible angle and direction northwards, then eastwards for around ten miles. Even drivers can feel car-sick on this one.
Respite is possible at the Achray Forest Drive (Toll) which is around six miles long, although you will emerge back on the A821 a mere mile and a half or so further on. Beyond the modestly picturesque Loch Achray is a short spur which leads to the lovely Loch Katrine and a progressively uglified tourist-spot, complete with gift shops, tea room and quad bike hire. This is a reservoir for Glasgow; on Bank Holidays it might as well be Sauchiehall Street gone north.
The main A821 then heads east along the banks of Loch Achray and the quaintly named Brig O'Turk (with a 40mph limit through the village). The next loch, Loch Venachar, is then met and the bank followed for some distance. The road has been improved in places but it is still water's-edge stuff at times and correspondingly winding. The road ends about two miles to the west of Callander - and yet another chance to pick up those last minute boxes of Edinburgh Rock, kilties in a bottle and tamed haggis. Throughout the route, traffic can be busy, even out of the main season, with coaches and mini buses crawling round the tight bends and struggling up the hills. Without any real overtaking opportunities, patience is necessary, but at least it allows you a better view of the surrounding scenery.
In 1922 the Dukes Pass appears not to have been suitable for motorised traffic, so only the A81 made the trip from Aberfoyle to Callander. However, work on improving the road was underway in the later 1920s, giving us the road we see today.
The original route of the A821 started at its current east end at Kilmahog, where it headed west along Loch Venachar and Loch Achray, to pass through the Trossachs and end on the shores of Loch Katrine (as it does today). In 1935 the road was extended from the shores of Loch Achray south along the Dukes Pass across the Achray Forest, to take on a short section of B829 and end on the A81. This history explains both the spur and the former TOTSO in Aberfoyle.