Final Answer:
Under adverse conditions, use the 4-second rule for measuring a safe following distance.
Step-by-step explanation:
The 4-second rule is a guideline for maintaining a safe following distance between your vehicle and the vehicle in front, especially under adverse conditions such as rain, snow, or poor visibility. To apply the rule, select a fixed point like a sign or a road marker.
When the vehicle ahead passes that point, start counting "one-thousand-one, one-thousand-two, one-thousand-three, one-thousand-four." If you reach the same point before completing the count, you are following too closely and need to increase your following distance. This rule provides a buffer, allowing you more time to react to sudden changes in the road or traffic conditions, reducing the risk of collisions.