"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'.