What is stopping sight distance (SSD)?

• A. The minimum distance a driver needs to perceive, react, and stop safely for a hazard.
• B. The distance a driver must travel before a vehicle ahead begins to slow.
• C. The distance required to accelerate to the posted speed.
• D. The distance to observe pedestrians at an intersection.

Answer: (A)

Stopping sight distance is the minimum distance a driver must be able to see ahead and safely stop when a hazard appears. It combines two parts: perception-reaction distance—the distance traveled from the moment you notice the hazard to the moment you start braking, which is speed times your reaction time—and braking distance—the distance your vehicle travels after you begin braking until you stop, which depends on speed and how quickly you can decelerate given road surface, tires, and conditions. As speed increases, both parts grow, and wet or icy pavement or a slope makes braking less effective, increasing SSD. The other ideas describe only one piece of the process—reacting to a vehicle ahead, accelerating to a speed, or observing pedestrians at an intersection—but none cover the full sequence of perceiving a hazard, reacting, and stopping.