How to Calculate Road Gradient

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The gradient of a road is a measure of how steep the road is. The gradient is sometimes referred to as the grade, incline, slope, rise or pitch. Automotive vehicles are rated in terms of the maximum grade they can ascend safely. Gradients can be expressed either in terms of a percentage or in terms of an angle, in degrees.

Place the ruler flat on the surface of the road so that it is parallel with the direction of the slope. Place the spirit level on top of it.

Raise the lower end of the ruler until the spirit level indicates that the ruler is horizontal.

Hold the plumb line alongside the raised end of the ruler. Note the point on the plumb line corresponding with the height of the raised end of the ruler.

Measure the length of the relevant section of the plumb line. This is the height of the horizontal ruler above the road surface. Make a note of this value.

Divide the value found in Step 4 by the length of your ruler. Multiply this value by 100. This final value will be the slope expressed as a percentage.

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