What is a main requirement for farm vehicles to travel on interstates?

The requirement for farm vehicles to travel on interstates primarily revolves around meeting specific safety criteria. This includes ensuring that the vehicles are equipped with all necessary safety features, such as proper lighting, reflectors, and any required safety equipment to maintain highway safety. Adhering to safety standards helps prevent accidents and enhances the visibility of farm vehicles, particularly because they are often slower-moving than regular traffic.

The other choices involve different aspects of regulation that may apply to farm operations or vehicle requirements but are not as directly tied to the capability of farm vehicles to travel on interstates specifically. While compliance with agricultural regulations, the need for commercial endorsements, and obtaining agricultural permits are important for various operational and legal reasons, they do not fundamentally address the primary requirement regarding travel on interstates, which focuses on safety measures.