If driving a 30-foot vehicle at 55 mph, how many seconds of following distance should you allow?

Answer: B — 4 seconds

The recommended following distance for a vehicle that is 30 feet long driving at 55 mph is four seconds. This guideline is based on the principle of providing ample time for reaction and stopping in emergencies. At higher speeds, stopping distances increase, and larger vehicles require more time to react and come to a complete stop. The four-second rule accounts for the vehicle's size and gives the driver enough time to respond to sudden changes in traffic or road conditions, ensuring safer driving. This time frame allows for the increased stopping distance associated with larger vehicles, like buses or trucks, thus promoting safety for both the driver and others on the road. In this context, options advocating for less than four seconds may not provide sufficient time, especially under more demanding driving conditions, making them less appropriate for a vehicle of this size and speed.