Civil Engineering PE

Answer: A - The controlling factor in the design of a 2-lane roadway sag vertical curve is the headlight sight distance. However, the stopping sight distance is most commonly used to design crest and sag vertical curves on a 2-lane roadway. Crest vertical curves are designed so that the crest does not obstruct the stopping sight distance. For a sag vertical curve, adequate vertical clearance must be provided where an overhead structure could obstruct the stopping site distance.