How much distance should you keep when following another vehicle?

Answer: B — At least one car length for every 10 mph

The guideline to maintain at least one car length for every 10 mph when following another vehicle is rooted in the principle of maintaining a safe following distance. This distance allows drivers adequate time to react in case the vehicle in front suddenly stops or slows down. For instance, if you are traveling at 40 mph, having four car lengths between you and the vehicle ahead contributes to reducing the likelihood of rear-end collisions, as it gives you space to manage your speed more effectively. This rule of thumb helps accommodate various driving conditions, including weather factors like rain or fog, where longer stopping distances might be necessary. It also accounts for the average reaction time needed when driving at higher speeds, reinforcing the importance of keeping enough distance to ensure safety.