What is the recommended following distance when driving behind another vehicle?

The correct answer is based on the principle of maintaining a safe following distance to allow for adequate reaction time in various driving conditions. A three-second following distance is generally considered a safe minimum; this gives drivers enough time to react if the vehicle in front suddenly stops or slows down.

This rule is calculated using a simple method: when the vehicle ahead passes a fixed point (like a sign or a tree), the driver should be able to count "one thousand one, one thousand two, and one thousand three" before reaching that same point. This technique accounts for the vehicle's speed—faster speeds require a greater distance—and conditions such as poor weather or road visibility, where a larger buffer may be advisable.

The other options either suggest an insufficient distance, which could increase the risk of a rear-end collision, or an excessive following distance that is impractical for normal driving conditions. A one-car length does not provide enough time for reaction, while a five-second rule might be overly cautious in typical circumstances. Thus, three seconds strikes a good balance between safety and practicality.