Final answer:
On a dry surface at speeds between 46 to 70 mph, the 3-second rule should be used to maintain a safe following distance, considering both reaction time and stopping distance. The correct answer is option C.
Step-by-step explanation:
When you are traveling at 46 to 70 mph on a dry surface, the appropriate rule to use is the 3-second rule. This means you should maintain a following distance that allows for at least three seconds of time between your vehicle and the vehicle in front of you. To calculate this, once you see the vehicle in front of you pass a stationary object, like a road sign, start counting seconds until your car passes the same point. If you count to three before reaching the object, you are following at a safe distance. If not, you need to increase your following distance.
This following distance needs to integrate the time it takes to react—known as the reaction time—and the distance your car travels during that time. For example, assuming a car traveling at 30.0 m/s (which is roughly 67 mph) has a reaction time of 0.500 seconds and an acceleration of 0 m/s² during reaction, the car travels 15.0 m while the driver is reacting. This distance must be taken into account when determining total stopping distances.
For dry conditions, using the 3-second rule allows drivers to account for both their reaction time and the stopping distance required to avoid collisions. It's crucial to remember that this following distance should be extended during adverse weather conditions or when driving on wet surfaces.