Elevation charts and percents

[Rebecca19804]

Thanks nikkoblu2 for posting this as I've been wondering the same thing!

A 45° angle (no such thing in roads AFAIK!) would be a 100% grade because the two sides of the right triangle are equal, as you travel the hypotenuse.

So Oakleaf, if I'm understanding this right, this example means:
45° angle = gain 1 foot in elevation in 1 foot of horizontal travel
= 1:1 grade [I get ratios ]
= 100% grade
= IMPOSSIBLE?!