map: little car symbol on some back roads?

[RootlessAgrarian]

I notice that on the map, some of the outback roads are marked with little yellow car symbols. At first I thought that this meant these roads are not passable with a trailer -- only cars and unloaded trucks can use them. But recently the game told me to deliver a trailer on such a road and I found that -- despite some tricky hairpins -- I could indeed get a trailer over it. So... what does the little car symbol mean, please?

[ETS2-User]

It says 4x4 so more then one powered axle is recommended there. Bad luck if you got a quick job with a 340hp Renault up there.

[Vøytek]

Those in Iceland are optional - GPS won't show you a route there
That one in Norway is really challenging and there's no other way to go around, so be prepared.

[RootlessAgrarian]

@ETS2-User: Oh interesting! so I have a very powerful engine and transmission, but only one powered axle. If I upgraded to "more wheels" then I would have an easier time on these roads? That would be worth the upgrade fee.

I didn't realise the sim was that faithful to reality (what was I thinking, this is ETS2). Are there negative consequences to upgrading to a dual-axle tractor? will I get higher fuel consumption, more expensive tire replacements, etc? I never bothered, despite having upgraded my truck to the max in every other respect, because I couldn't figure out how to make an intelligent choice of lift-axle configuration, etc. Unable to choose, I just stuck with my basic tractor. Which configuration of rear wheels do others recommend?

Maybe this is why I've been having trouble on steep grades with snow!

@Zniwek: that Norway back road was an absolute treat. One of the great ETS2 gameplay moments, actually. I sang its praises on the OT "thanks" thread. And I did manage to get an extra-long trailer (heavy equipment delivery) all the way to Nordkalk without any damage, that felt like an achievement

[Vøytek]

When I installed more axles on some trucks, I had smaller fuel tanks, so I had to refuel much more often. Maybe some other things change too, probably fuel consumption. But I'm not sure, so don't trust my words

That road is awesome. Best challenge in this map. When beta-testing, I was able to drive from dam to Kirkenes, with 4x2 Scania. One spot was really hard but after 10 minutes of maneuvering, I did it