What is the purpose of a vertical curve in road design?

A vertical curve in road design serves the critical function of connecting different grades or slopes of the roadway. This transition is essential for ensuring a smooth change in elevation, allowing vehicles to ascend or descend without abrupt changes that could compromise safety and driveability. Vertical curves help improve the overall driving experience by enhancing visibility and comfort, minimizing sudden changes in gradient that could lead to loss of control or discomfort for drivers and passengers.

The design of vertical curves also plays a crucial role in adequate sight distance, ensuring that drivers can see ahead and make safe decisions as they approach grade changes. This is particularly important in areas like hills or embankments.

The other options do not pertain to the specific function of vertical curves. While measuring land elevation is important in overall road design, it is not the purpose of a vertical curve. Similarly, drainage methods and determining road width involve different design elements unrelated to the transition between grades.