I live at the top of a common driveway that's 1/3 - 1/2 mile long. According to my neighbor, it's a 10% grade (Now I'm thinking that I want to measure it). At least, it's steep enough that it will never be declared a public road that the town will take over maintenance on.
I can make it up, but I'm not sure I could imagine doing it for a longer distance at this point.