CST Level 1 Land Surveyor Certification Practice

When analyzing a road profile, the curve in question typically refers to the variation in elevation along the route. A vertical curve is used in road design to connect two different grades, ensuring a smooth transition for vehicles.

In road design, vertical curves can be classified as either crest curves or sag curves. Crest curves occur at the top of a hill where the grade changes from a rising slope to a falling slope, while sag curves are at the bottom of a dip where the grade shifts from falling to rising. Properly designed vertical curves are essential for visibility, safety, and comfort of drivers as they traverse changes in grade.

The other types of curves mentioned—horizontal, spiral, and reverse—serve different purposes in road geometry. Horizontal curves are related to the road's alignment on a horizontal plane, and spiral curves are gradual transitions between straight and curved sections. Reverse curves consist of two curves that bend in opposite directions and are typically not analyzed in the context of elevation changes.