Did you know that the Days Gone originally had Deacon St. John singing this "Making my way downtown, walking fast, freakers pass and I'm homebound, staring blankly ahead just cutting my way, making a way through the crowd."? (this is in our headcanon)
Well, it turns out that the world of Days Gone is pretty brutal. Who knew that trying to survive after an apocalypse would be stressful eh? The world is pretty much constantly trying to kill you, so figuring out the right way to make your life easier, and more importantly safer, should be an early port of call.
If you want to spend hours riding through the mindless hordes then you can do so. If, however, you would rather zip around unimpeded, then you can use the fast travel system. Not the bike, the even faster travel system, the instant one.
You'll unlock fast travel points as you journey around the world and can see and select them on the map. You can only go to places you've already been, and even then there are a couple of rules you need to follow. Nothing is ever simple after the world has ended is it? Can't even get a decent cup of coffee without trading in a hundred freaker ears. Ugh.
Anyway, the restrictions that come in to play with fast travel are that first of all, it costs fuel. Whenever you highlight somewhere for fast travel it will let you know how much fuel will be used up. You're going to need to plan accordingly. Simply doing it without thinking will end up stranding you.
The other factor to keep in mind is that you need a clear path from where you are to where you want to go. This means that you have to clear out any Infestation Nests that are on your path. Otherwise, you can't do it. Just keep these things in mind when trying to fast travel.