The term "grade" is used in several different ways with respect to roads and highways. The "sub-grade" lies beneath a roadway and is used as a supporting base. "Grading" a road means to smooth out the roadbed with earthmoving equipment during the construction phase. In this article, the grade of a road is defined as a measure of the road's steepness as it rises and falls along its route. In other words, it is the magnitude of its incline or slope.

The grade of a highway is a measure of its incline or slope. The amount of grade indicates how much the highway is inclined from the horizontal. For example, if a section of road is perfectly flat and level, then its grade along that section is zero. However, if the section is very steep, then the grade along that section will be expressed as a...