What aspect of a road does a vertical curve primarily address?

A vertical curve primarily addresses changes in grade along a road. These curves are essential components of road design, as they create a smooth transition between different slopes or grades. This is particularly important for ensuring driver comfort and safety, as abrupt changes in grade can lead to visibility issues, instability, or a jarring experience for vehicles.

Vertical curves can be either crest (where the road rises) or sag (where the road dips), and they influence various aspects of road performance, including sight distance and stopping distance. By effectively managing changes in grade, vertical curves facilitate safer navigation through varying terrain, improving overall road ergonomics for drivers and vehicles alike.