Which of the following vehicles must have mud flaps when operated on public roads?

Mud flaps are important safety features designed to reduce the amount of road debris and water that gets kicked up by vehicle tires, which can affect visibility for other drivers and lead to accidents. The correct answer indicates that all vehicles with four or more tires on the rear axle must have mud flaps when operated on public roads.

This requirement generally aims to ensure that larger vehicles, which have the potential to cause more significant damage or visibility issues when throwing debris, are equipped with appropriate safety measures. Vehicles with multiple tires on the rear axle, such as large trucks and some recreational vehicles, pose a greater risk in creating a hazardous environment for other road users if they do not have mud flaps.

The other options provided do not encompass the broader range of vehicles that might need mud flaps or are too specific. For example, not all passenger vehicles or those with a single rear axle would be subjected to the same regulations regarding mud flaps, as these vehicles generally have less impact on projecting debris as compared to vehicles with multiple rear tires. Therefore, the requirement for vehicles with four or more tires on the rear axle effectively covers a significant portion of vehicles that could potentially cause such hazards on the road.