Grade of a Road

Today I'll be explaining grades of roads. Determining the correct grade of the road on a highway is extremely important to the safety of the motorists and drivers who drive on a certain road with a grade. The grade of a road is determined by the simple ratio of "rise over run." The grade indicates how long you must travel up or down a road for a vertical rise or drop of a foot. The rise is the change in vertical distance and the run is the change in horizontal distance. In short, the grade of roads are measured by the slope or incline of distance traveled. When you see grade signs on the sides of roads or highways, they're expressed in percentages. "x%" grades show the percentage of grade the road has. To find the percentage of the road, you simply multiply the decimal grade by "100". 





 Grade and slope are very closely related. In terms of finding the incline or slope of a road, they both measure the steepness. The slope shows the direction and the steepness of a line, and slope can be measured in grades, as this topic of measuring the grade of roads. Trigonometry then relates back to both grade and slope as you can find the angle of elevation by using the inverse tangent.

 The steepest road in the world, Baldwin Street in Dunedin, New Zealand has an average grade of 20% and at it's steepest point, has a 38% grade!! This is seriously steep and I would personally like to try riding up it on a bike!







Photo of Baldwin Street:

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