Final answer:
To increase the recommended safe following distance, you can either increase the distance or reduce the time. Increasing the distance by fourfold while keeping the time constant or keeping the distance constant and reducing the time by one-fourth.
Step-by-step explanation:
In order to give an extra margin of safety, you would need to increase the recommended three-second safe following distance. This can be done by either increasing the distance or reducing the time.
Option 1: Increase the distance by fourfold while keeping the time constant. For example, if the initial distance is 10 meters, the increased distance would be 10 meters x 4 = 40 meters.
Option 2: Keep the distance constant and reduce the time by one-fourth. For example, if the initial time is 3 seconds, the reduced time would be 3 seconds / 4 = 0.75 seconds.