^ Agreed. Average is the wrong concept. More of a histogram that shows distribution about the median grade on the independent (horizontal) axis, and the steepness of the grade in % on the dependent axis. The grade length would need to be fixed for measurements, because a rolling average would round off the steeper/more-rapidly changing sections. So, it'd be distribution function of grades relative to other grades. This would give a picture of the roadways within a city. It'd be a lot of measuring to do, though.