If you are traveling at 55 mph in a 30-foot vehicle, how many seconds of following distance should you leave?

When determining the appropriate following distance for a vehicle, particularly a larger vehicle like a 30-foot truck, it's essential to consider the speed of travel. At a speed of 55 mph, a following distance of four seconds is recommended. This is because larger vehicles require more time and space to respond to sudden stops or changes in traffic conditions due to their size and weight, which affects their braking distance.

A four-second following distance provides a buffer that allows the driver to react safely and gives sufficient time to stop in an emergency without colliding with the vehicle ahead. This distance is a general rule of thumb that helps ensure safety at higher speeds, where stopping distances greatly increase.

For vehicles like trucks, additional caution is advised, and the four seconds in this scenario helps account for their possible longer stopping distances. The other options, while they may be suitable for smaller vehicles at similar speeds, do not provide adequate time for the 30-foot vehicle, which has different handling characteristics and requires a larger safety margin.