CDL Vehicle Combination Practice Test

The glad hands are the couplings that connect the air supply lines between the trailer and the tractor. They are crucial for the functioning of the trailer's air brake system. Ensuring that the glad hands are clean and dry is vital because dirt or moisture can interfere with the air supply and performance of the braking system. Contaminants in this area can cause air leaks, which might lead to brake failure or reduced braking efficiency.

Checking the glad hands when not towing helps to maintain the integrity of the air system, ensuring it is functioning properly when the trailer is attached. Neglecting this inspection could result in significant safety hazards while on the road due to compromised braking performance.

While it's also critical to check the tires, brakes, and interior of the trailer for their own safety and operational reasons, the specific importance of the glad hands in maintaining proper air flow and brake function makes them particularly essential to examine for dirt and moisture when not towing.