What is the proper following distance for CMVs traveling over 40 mph?

The appropriate following distance for commercial motor vehicles (CMVs) traveling over 40 mph is based on both time and length considerations. The correct approach detailed in option C emphasizes the importance of maintaining a safe distance not just for the speed of the vehicle, but also for the size of the vehicle itself.

The guideline suggests starting with a baseline of 1 additional second following distance, which provides a buffer for reaction time at higher speeds, and then adds another second for every 10 feet of vehicle length. This is particularly crucial for CMVs, which can be significantly larger and heavier than standard vehicles. The longer a vehicle is, the longer it will take to stop, and therefore, a greater following distance is necessary to prevent collisions.

This method of calculating following distance balances the need for safety with practical driving considerations. By ensuring that drivers of larger CMVs are aware of their vehicle's size and the impacts on stopping distances, option C helps promote safer driving practices during highway travel, which is vital given the risks associated with heavy trucks on the road.