What must a vehicle do when following another vehicle?

The requirement for a vehicle following another vehicle is to keep a safe distance that allows for sufficient space should the lead vehicle suddenly stop. This concept of maintaining a safe following distance is crucial for ensuring that a driver has enough time to react in case of an emergency. The standard recommendation is usually at least one car length for every ten miles per hour of speed, meaning that the distance should increase with higher speeds to accommodate for factors such as reaction time and the stopping distance of the vehicles involved.

This option emphasizes the necessity of having a buffer zone between vehicles, which is essential for safety on the road. By having that space, a driver can avoid collisions, especially in scenarios of abrupt braking or unexpected obstacles. The other options do not align with the critical need for flexible and situationally aware driving practices; they suggest either arbitrary distances, unnecessary restrictions on lane changes, or dangerous speeding behaviors that compromise safety.