Absolute minimum sight distance of Road

Safe stopping sight distance, SSD for the design speed is the absolute minimum sight distance. This particular sight distance traveled during perception-reaction time, and maneuver time. Actual stopping distances are also affected by road conditions, the mass of the car, the incline of the road, and numerous other factors. For design, a conservative distance is needed to allow a vehicle traveling at design speed to stop before reaching a stationary object in its path. Typically the design sight distance allows a below-average driver to stop in time to avoid a collision.