"as long as they exist" probably was the wrong term to use. They exist the whole way out, but what state of repair they are in will become the issue, to the point where they may not be much if any better than being off them.
It is basically balancing an increased profile for speed. Granted if you get spotted by the wrong party way off the road, it may be hard to explain why you are there.
There are potential (though different) risks traveling either way.
Also: To avoid being overly mean to the players: CS since you took an attack action, realize you are aquiring overwatch score at regular intervals atm.