What is the primary function of a vertical curve in roadway design?

What is the primary function of a vertical curve in roadway design?

• A. To increase pavement thickness.
• B. To reduce cross-slope.
• C. To change horizontal alignment.
• D. To provide a smooth transition in grade for sight distance and driver comfort.

Answer: (D)

Vertical curves are used to connect two different grades with a smooth, gradual change in slope. This gradual transition is essential for sight distance and driver comfort, since abrupt changes in grade can surprise drivers, affect stopping and acceleration, and create an uncomfortable ride. So the primary function is to provide a smooth transition in grade that supports adequate sight distance and a comfortable, predictable driving experience. The other options don’t fit because pavement thickness is set by structural design, cross-slope is managed separately from vertical transitions, and horizontal alignment is adjusted with horizontal curves, not vertical ones.

Vertical curves are used to connect two different grades with a smooth, gradual change in slope. This gradual transition is essential for sight distance and driver comfort, since abrupt changes in grade can surprise drivers, affect stopping and acceleration, and create an uncomfortable ride. So the primary function is to provide a smooth transition in grade that supports adequate sight distance and a comfortable, predictable driving experience. The other options don’t fit because pavement thickness is set by structural design, cross-slope is managed separately from vertical transitions, and horizontal alignment is adjusted with horizontal curves, not vertical ones.