What is required when a vehicle is towed on a controlled-access highway?

Using a drawbar when towing a vehicle on a controlled-access highway is essential for safety and stability. A drawbar is a heavy-duty connector that links the towing vehicle to the trailer or towed vehicle, providing a secure attachment and allowing for safe maneuvering at higher speeds. This is particularly important on controlled-access highways, where vehicles may travel at higher speeds compared to local roads, thus requiring additional security measures to prevent detachment or wobbling during transit.

In contrast, other answer choices do not meet the same critical safety requirements. For example, not exceeding a speed of 10 mph is impractical for highway conditions, and there is no general regulation that mandates the towed vehicle must be empty. Additionally, using only one safety chain does not provide adequate safety assurance; typically, two safety chains are needed for adequate redundancy, ensuring that the towed vehicle remains secure even if one chain were to fail.