In terms of vertical curve design, where is the elevation of the Point of Vertical Intersection (PVI) in relation to the highest point on a crest vertical curve?

In vertical curve design, the Point of Vertical Intersection (PVI) represents the point where two roadway grades meet. For a crest vertical curve, the highest point occurs at the midpoint of the curve, where the road transitions from an uphill grade to a downhill grade.

The elevation of the PVI is always higher than the elevation of the highest point on a crest vertical curve. This is because the PVI is located between the two tangent grades that form the curve. As the road ascends to the highest point, it reaches a peak before descending again. Thus, the PVI, which is the point of grade intersection, must be positioned higher than the curve’s highest elevation to ensure a smooth transition in elevation from ascending to descending.

Understanding this relationship is vital in roadway design, as it affects visibility, drainage, and overall road safety. The correct alignment ensures that vehicles can navigate changes in elevation smoothly without experiencing abrupt changes in gradient.