Stopping sight distance factors include which of the following together?

• A. Vehicle speed.
• B. Driver's perception-reaction time.
• C. Braking capability.
• D. Vehicle speed, perception-reaction time, braking capability, and road conditions.

Answer: (D)

Stopping sight distance is the total distance a driver needs from the moment they notice a need to stop to the moment the vehicle comes to a complete stop. It combines perception-reaction distance (what the driver covers while noticing the need to stop and deciding to act) and braking distance (how far the car travels while decelerating). Perception-reaction distance depends on how fast the vehicle is going and how long the driver takes to react. Braking distance depends on how quickly the car can decelerate, which is governed by braking capability, and this in turn is strongly affected by road conditions that change the friction between tires and surface. Since higher speed increases both perception-reaction distance and braking distance, and because braking capability and road conditions can greatly alter how quickly the car slows, all four factors—speed, perception-reaction time, braking capability, and road conditions—together determine the stopping sight distance.