Well there is a slight difference with "further" and "farther". The correct use when talking about physical distance is "farther". So when I say to someone "The hotel is farther up the road", I mean that whoever I am talking to needs to continue traveling along the road to get to the hotel. In English "It's father up..." or "It's farther down..." is commonly used even though there may not be any change in height or altitude.

"It's further up the road" = It is past here, along the road in the direction you are traveling. You could also say "down the road" - there is no logic to it. If you are looking at a map, "up" usually means north, while "down" usually means south. However, if I were giving you directions, I might not know exact north and south. I might just say 'up' or 'down' depending on how I felt. One rule - if you are going up in elevation, I would definitely say 'further up'.