It wasn't to get to their destination, this road isn't on any maps and ends on the top of the mountain.
Its usually a certian religious group looking for houses to witness to. But they compeltely ignore the sign that says private drive no trespassing so even though this road is closed. I could see the same thing happening in a situation such as this, someone thinks they need to go through a gate that says road closed so they ignore the sign/warning and go through.