On which valves should the towing trailer valves be and the trailer in-tow valves be?

When towing a trailer, the configuration of the valves is crucial for safe and effective operation. The correct answer indicates that the towing trailer valve should be open while the trailer in-tow valve should be closed. This setup ensures that the air supply can properly flow from the towing vehicle to the trailer's braking system, which is essential for providing adequate stopping power.

By keeping the trailer in-tow valve closed, it prevents air from escaping or creating a potential leak in the trailer's system, allowing the brakes to function correctly without risking a failure. In contrast, the open towing trailer valve facilitates the connection and communication between the truck and the trailer, enabling the braking system to respond appropriately to the driver's inputs.

This arrangement is crucial during driving; it ensures that the trailer brakes engage when needed, improving overall safety and control while on the road. Proper understanding and handling of these valves are vital for all those involved in towing, as incorrect settings can lead to hazardous situations.