But in such remote areas, where public transport is sparse at best, the postal service delivers not only mail but also people, both locals and tourists.
Since the first Post Bus trundled off from Llanidloes to Llangurig in 1967, this little-known transport service has grown steadily to over 200 routes nationwide. While coverage remains patchy in England and Wales, the network now extends across most of rural Scotland where, for the tourist, they provide a novel and cost-effective way to get around.
The down side of Post Bus travel is that because they often serve isolated communities, it's not always possible to find connections for exactly where you want to go. But if you study the timetables carefully there are plenty of rewarding journeys.
On a recent trip to Scotland I spent a few days doing the rounds through Hamish McNab's patch. Route F13, for example, leaves the village of Lairg for a 60 mile journey to Durness, the most north-westerly village on the British mainland. Seats cost just pounds 4.65 and are allocated on a first-come- first-served basis (though parcels take priority over people).
Within a few minutes of leaving Lairg we were bouncing along a single- track lane through a wilderness of green gorse. It was here that the most notorious evictions took place during the highland clearances and, almost two centuries later, there is still no one here. We stopped just twice on the lonely run north until we reached the coast - once to hand some post to that passing motorist.
The first community of any size along the route is Tongue, a crofting settlement nestling on the rim of a narrow kyle. With a Post Office, shop, Youth Hostel and two hotels, it's a veritable metropolis and makes a good overnight stop for Post Bus travellers heading east on the chain of routes that deliver to Bettyhill, Melvich, Dounreay, Thurso, Wick and John O'Groats.
Outside the summer months Post Buses are the only form of public transport along much of the north coast. Postmen are not obliged to act as tour guides, but inevitably anything of interest is pointed out. Route F13's features include Loch Eriboll, a spectacular finger of sea that is home to otters, porpoises and even Minke whales, and the farm where Alan Clark MP is said to keep a collection of tanks.
Stepping off at Durness, 30 contorted miles west of Tongue, it's easy to understand why the Post Bus is such a lifeline. Little more than a scattering of white-washed houses, this is literally the end of the road. If you want to travel any further north-west on the mainland you'll have to make a short ferry crossing across the Kyle of Durness and follow a narrow track that winds out to Cape Wrath light house.
It is Cape Wrath, in fact, that lures most tourists to this corner of Britain. When I visited, the RAF were tossing live ordnance at an unfortunate outcrop of rock close by and, sadly, access was restricted. But by all accounts, the highlight is not the massive sea-cliffs of the Cape itself, but Sandwood Bay, a six-mile hike to the south. Make the effort to reach what is said to be the most isolated beach in Britain, and it's likely you'll have this beautiful white-sand bay to yourself.
If you can't reach Cape Wrath, Durness has an excellent visitors' centre with leaflets aplenty telling you how to explore the area, which includes peat tracks, sand dunes and puffin colonies. Leaving Durness, Post Bus travellers can then board the F43 which takes the west coast route back to Lairg through Kinlochbervie and Scourie. On this part of the west coast progress can be quite slow as the routes often branch off along dead-end tracks to reach isolated communities. Frustrating for locals in a hurry, but perfect for visitors who get to pootle through some stunning scenery.
Despite an absurdly beautiful coastal location, Kinlochbervie's economy is built around commercial fishing and the village has few amenities for tourists. Scourie, on the other hand, has a number of places to stay, as well as a beach, fishing and boat trips to Handa Island bird sanctuary.
Heading back inland towards Lairg the route wanders through the Duke of Westminster's estate - 400,000 acres of Scottish wilderness. We pulled up only when an orange flag fluttering from a post-box indicated that mail needed collecting, and for another roadside delivery to a passing motorist. This time the mail comprised a bunch of garish leaflets. Even in the Highlands of Scotland there's no escaping junk mail.
Five separate regional timetables cover Scotland's Post Bus network. They are available from Tourist Information Centres or from: Post Office Publications, 130 Old Street, London EC1V 9PQ (0171-614 7153). A public transport map of the Highlands, including Post Bus routes, is also available from Inverness Tourist Information Centre on 01463 234353.