Sight distance on vertical curves is critical in roadway design. It ensures drivers can see far enough ahead to identify and respond to hazards effectively. This directly impacts safety, driver comfort, and the overall efficiency of the transportation network.

Vertical curves are classified into crest and sag curves based on their geometry. For crest curves, sight distance is determined by the line of sight between a driver's eye and a small object on the road's surface. Design parameters for sight distance include the height of the driver's eye and the height of the object being observed. According to design guidelines, these parameters are typically assumed to be 1.07 meters and 0.61 meters, respectively. Meanwhile, for sag curves, sight distance depends on the reach of a vehicle's headlights at night, ensuring obstacles are visible in time for a safe reaction. 

Stopping sight distance (SSD) further influences the design. SSD is the minimum distance required for a vehicle to stop safely, and depends on factors such as reaction time, vehicle speed, braking performance, and the condition of the road surface. For sag curves, the visibility provided by vehicle headlights is critical at night, requiring proper curve design to extend the beam of light along the roadway. In addition to sight distance, sag vertical curves must be designed with rider comfort and drainage in mind. Excessive vertical acceleration at the bottom of sag curves can cause discomfort, while inadequate drainage can lead to water accumulation. Properly designed curves balance these factors, ensuring smooth transitions and safe driving conditions.