I used to be scared of flying (technically still am but I’ve since learned to manage that fear) so over the years I’ve travelled great distances by road and rail. I’ve used coaches a lot to travel the U.K. and Europe. 12 hours has taken me from London to Amsterdam. I’d wager another 12 hours would get you as far as Eastern European, possibly even Russia.
But such a journey would have to be pre-booked coaches. You couldn’t get there on buses.