The percent grade of a highway is the amount that the highway raises or falls in a given horizontal distance. For example, a highway with a four percent grade rises 0.04 mile for every 1 mile of horizontal distance.

Question

a. How many feet does a highway with a six percent grade rise in 2.5 miles of horizontal distance?
b. How many feet would a highway with a six percent grade rise in 90 miles of horizontal distance if the grade remained constant?
c. How is percent grade related to slope?

Answer 1

a. Y/X = Y/2.5 = 0.06
Y/2.5 = 0.06
Y = 0.15 Miles = 792 Ft.

b. Y/X = Y/90 = 0.06
Y = 90 * 0.06 = 5.4 Miles = 28,512 Ft.

c. % Grade = Slope expressed as a decimal.

Answer 2

Correction:
c. % Grade = Slope expressed as a percentage.