What must a trailer have if it is towed by a vehicle?

A trailer towed by a vehicle must have fenders, covers, or devices to ensure safety and compliance with regulations. These features are designed to prevent debris and water from being thrown up by the tires while the trailer is in motion, which can pose a hazard to other road users. Fenders are essential for protecting both the trailer itself and other vehicles or pedestrians from potential damage or injury caused by objects dislodged from the trailer's tires.

In contrast, while having an additional towing vehicle, more than one axle, or a special permit may be relevant in certain contexts, they do not represent a generalized requirement for every trailer being towed. The fundamental aspect of ensuring safety and minimizing risks on the road focuses on the necessity of having appropriate fendering or similar protective devices.