Civil Engineering - Surveying - Discussion

A rising gradient of 1 in 40 is to be connected with a falling gradient of 1 in 75 by means of a vertical equal tangent parabolic curve 400 m in length. The reduce level at the intersection point of the tangent is 26.850.

Calculate:

(1) The rate of change of grade.

(2) The reduced levels at the beginning and end tangent points.

The main design criteria in a vertical curve is headlight sight distance. So I think it may be circular as the sight distance available at each point is same.

Because rate of change of gradient in parabolic curve is constant.

So generally used parabolic type of curve.

The gradient is nothing but a slope. And the best way to join 2 gradients using a vertical curve is obviously using a parabolic one.

Why it is parabolic?

Give me an accurate answer.