As I've said before - I know that area very well.
Are you one of the fisherman found in summertime?
It isn't really a long drive if you think about it... you could do it really fast depending on what time you drive there, but as I've said before I'm sure the killer stayed in the limits and didn't speed as they wouldn't want to be picked up by the cops for speeding.
Also, when the floods hit in January 2011, Kholo Creek got to a massive 18+ metres and there was no bridge. Only recently has all the flood debris fallen from the trees at this overpass.