What unsatisfactory situation could arise from a lack of adequate following distance?

A lack of adequate following distance can lead to an increased risk of rear-end collisions. When a driver does not maintain an appropriate distance from the vehicle in front, they may not have sufficient time to react to sudden stops or changes in speed. This lack of reaction time can result in not being able to stop in time, causing a crash. Maintaining a safe following distance allows drivers to see the stopping behavior of the vehicle ahead and respond appropriately, significantly reducing the likelihood of collisions.

In contrast, the other options do not directly correlate with the issue of following distance. While a longer trip duration may occur under various circumstances, it is not inherently caused by following distance. Better fuel efficiency could be achieved with proper driving behavior but is unrelated to maintaining distance from other vehicles. Lastly, less driver focus may arise from various factors, but it is not a direct effect of having insufficient following distance. Therefore, the relationship between following distance and the risk of collisions highlights the importance of maintaining a safe distance on the road.