Which of the following does not require a Commercial Driver's License (CDL)?

Recreational vehicles (RVs) typically do not require a Commercial Driver's License (CDL) as long as they fall within certain weight limits and are not used for commercial purposes. Most states classify RVs as personal vehicles, which usually means that a regular driver's license is sufficient for operation.

On the other hand, passenger buses, heavy trucks, and school buses are classified as commercial vehicles that generally require a CDL to operate due to their size, weight, and the potential for carrying multiple passengers or hazardous materials. The necessity of a CDL for these vehicles is rooted in the need for specialized training and stricter regulations to ensure safety on the roads.