Even better is the accuracy of the return trip:
OK, so lets start with Australia, Great Britain, Ireland, New Zealand, Japan, yawn
(Oh, bugger, the OP did also say North America…OK, then, Bermuda, Greenland…)
I’m considering two islands for very specific reasons.
Consider Molokai. The island’s road system is divided in 2. The main part of the island is seperated from the defunct county of Makawao (Kalaupapa) which has it’s own road system. The only thing I know that connects the two is a hiking trail. Observe this photo to see why.
Also of interest are various roads on the Big Island which due to lava flows are no longer reachable.
pic 1
pic 2
I assume no one has bothered to restore access to at least some of those.
http://www.seldovia.com/nav_mapsaerial.htm
Seldovia is not an island. It is a whole town here with roads and even more roads than than listed in this site.
It is on the mainland and not an island and not in south east alaska. Only way to get there is by plane or boat.
http://www.seldovia.com/nav_towntour.htm
This is funny
2000 Census: 284 in-town residents, 100+ out-of-town residents, 50 resident eagles
They counted the eagles in their population
Australia has an interesting road between Victoria and Tasmania Spirit , at least the goverment considers it a highway althought I can’t locate a cit online.
Well, the OP was intended to recognize that of course there are islands that people live and drive on, and unless there’s a bridge, you cannot drive to and from an island without taking a ferry.
I was somewhat more interested in the idea that: (1) You can get, at least in theory, from Colon, Panama to Halifax, NS, and Anchorage, AK, and most points in between, by car; but (2) there are places on the North American mainland that have roads and vehicles, but that you cannot travel between them and the main highway grid covered in #1 by normal four-wheeled self-propelled transportation. What are these “road network islands” in the sense bup defined the term, where are they, and why do they exist as they do without linkage to the main grid?
This isn’t a 100% complete break, but might as well be…
In Northern Norway, just south of where the Lofoten Island chain juts out into the sea, we find a large inlet called Vestfjorden, which very nearly cuts the country in two. Vestfjorden, and particularly an arm of it called Tysfjorden, effectively bisect the Norwegian road network. There’s no road around it, no bridge over it - you must cross by ferry here.
It’s not a complete break, as if you’re allergic to ferries you can take the long way 'round through Sweden - but it is one hell of a detour.
I know Alaska’s been done to death, but you can’t drive to Barrow either, although there’s plenty of roads there. The gas gets shipped in once a year.
Yaviza, in the Darién, is the end of the road and farthest point that can be driven to normally.
As an aside, there have been at least four crossings of the Darién Gap by cars that I am aware of (plus a number by motorcycle). However, all but one involved ferrying the vehicles across the Atrato Swamp in Colombia by raft. Loren and Patrica Upton crossed the Gap in a Jeep entirely by land between 1985 and 1987. It took them three years because they could only travel during the four-month dry season.
This reminds me of when Microsoft’s map software directed you through England, France, the Low Countries, Germany, Denmark and Sweden just to get from Oslo to somewhere across that gap. Snopes.
Isolated villages in Alaska aren’t confined to the SW. There are dozens of villages all over the interior that are accessable only by air or by river.
I know the OP mentioned North America only but I do believe that I’ve been to a town that is considered the largest city not connected to any other area by road. On the border of of Columbia and Brasil (plus Peru) are the twin municipalities of Tabatinga and Leticia with a combined population of over 100,000. You can get there by the international airport or by ferry up the Amazon. It is also notable that Leticia is probably the safest city in Columbia (and the only place I’ve been in Columbia) because it is a little jungle tourist town completely isolated from rebels and drug dealers. Cool place, I stayed in a jungle hotel and fished for pirhana, which are the easiest fish on the planet to catch.