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This endorsement is required if the driver will pull two or three trailers. To receive this endorsement, applicants must pass a..

This endorsement is required if the driver will pull two or three trailers. To receive this endorsement, applicants must pass a test. The test consists of 20 multiple choice questions. To pass, the applicant must answer at least 16 questions correctly. Each question has four possible answer choices. Test questions come from the Washington D.C. Commercial Driver License Manual. Questions come from chapters covering: Driving Safely, Air Brakes (if applicable), Combination Vehicles and Doubles and Triples. The Double/Triple endorsement can be used with the Class A CDL.

Passing grade:

If the low pressure warning light comes on while you are driving:

Explanation
When driving a vehicle with air brakes, if the low air pressure warning light comes on, it is important for you to stop and safely park your vehicle as soon as possible. There may be a leak in the system. Controlled braking will remain possible only as long as there is enough air left in the tanks.

After connecting the air lines to the trailer while coupling, you should:

Explanation
Correctly following the steps to couple and uncouple trailers is vital to safely operating a combination vehicle. After connecting the air lines to the trailer while coupling, you should supply air to the trailer.

When traction is poor, a driver should accelerate slowly:

Explanation
Speeding up too quickly on a road with poor traction could cause a driver to lose control of their vehicle. In conditions that cause poor traction, a driver should accelerate especially smoothly and gradually.

If the spring brakes are activated, you should never:

Explanation
Never apply the brake pedal if your spring breaks are activated. Brakes can be damaged if they are subject to both springs and air pressure.

When stopped on the side of the road, the driver should:

Explanation
If you must stop on the side of the road, it is important to turn on your four-way emergency flashers to warn other road users.

A vehicle inspection is required:

Explanation
Federal and state laws require that CMV drivers inspect their vehicles before every trip.

Friction inside a brake drum is caused when the brake shoes and linings:

Explanation
Friction inside a brake drum is caused when the brake shoes and linings push against the inside of the drum. The friction in the drums will slow and stop the vehicle.
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