The number of trailers that may be pulled by one vehicle on the open highway is determined by:

The correct answer focuses on length limits, which are a key regulatory factor concerning the number of trailers that can be towed by a single vehicle on the open highway. In Texas, as in many other states, laws specify limits on vehicle length for safety reasons, ensuring that vehicles do not exceed certain dimensions that could affect maneuverability and visibility on the road.

Length limits set forth by transportation authorities determine how many trailers can be legally attached based on the overall length of the vehicle plus the trailers. This regulation is essential for preventing accidents and maintaining road safety, as longer combinations can be harder to control and more difficult for other drivers to navigate around them.

Although driver's experience, vehicle model, and weight limits are also important considerations in the safe towing of trailers, they do not specifically dictate the number of trailers that can be pulled. Experience can enhance the driver's ability to manage a given setup, while vehicle model influences the towing capacity. Weight limits are crucial for ensuring the safety of the vehicle and load but do not directly relate to the count of trailers that can be pulled, as these limits are more concerned with the gross weight of the combination rather than its length. Therefore, length limits are the decisive factor in determining how many trailers a vehicle can tow legally on the