CDL Combination Vehicles Practice Test 2

Question 1

The trailer protection valve is designed to close automatically if the air pressure reaches the range of

Accepted Answer

20 - 45 psi

Answer

The trailer protection valve is designed to automatically close and seal off the tractor's air supply to the trailer if the air pressure drops too low. This typically occurs when the air pressure falls into the range of 20-45 psi. This mechanism prevents a trailer air leak from completely depleting the tractor's air brake system.

Question 2

You should always test the trailer brakes before driving by

Accepted Answer

Options 1st & 2nd

Answer

Before driving, you should always test the trailer brakes using both the hand valve and by pulling the air supply control. The hand valve allows you to apply only the trailer brakes to check their function. Pulling the air supply control (which applies the trailer's emergency brakes) and then pushing it in while listening for air flow also confirms proper connection and function.

Question 3

If you are parking a trailer without spring brakes, which of the following should you use?

Accepted Answer

Wheel chocks

Answer

For trailers without spring brakes, wheel chocks are absolutely necessary when parking. Spring brakes automatically apply when air pressure is lost, but trailers without them rely solely on air pressure to hold the brakes. Without spring brakes, the trailer could roll away if the air pressure leaks down, making chocks vital for safety.

Question 4

The coupling device used to connect the service and emergency air lines from the truck to the trailer is known as?

Accepted Answer

Glad hands

Answer

Glad hands are the coupling devices used to connect the service and emergency air lines from the tractor to the trailer. They are designed to create an airtight seal, allowing air pressure to flow between the two vehicles for proper brake operation. Their distinctive 'handshake' shape gives them their name.

Question 5

Which of the following is a valve used at the back of a trailer that allows the closing of the air lines when another trailer is not being towed?

Accepted Answer

Cut-out cocks

Answer

Cut-out cocks are valves located at the back of a trailer, specifically designed to close off the air lines when another trailer is not being towed. This prevents air from escaping from the open lines, maintaining proper air pressure in the brake system of the single trailer. They are essential for proper air system management in multi-trailer operations.

CDL Practice Test

CDL Practice Test

CDL Combination Vehicles Practice Test 2