Instructions

Double

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.. Read More

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 two, three or four possible answer choices. Test questions come from the South Carolina 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.

Number of Question 20

Passing Score 16

1. Rims with welding repairs:

Are unsafe.

Are acceptable on tires in the rear of the vehicle.

Are acceptable only when carrying a heavy load.

Are acceptable in combination vehicles.

A driver should inspect wheels before a drive, specifically looking for damage on the wheels and rims. Wheels or rims that have had welding repairs are not safe for use.

2. Backing with a trailer is dangerous because:

It is difficult for the driver to see behind the trailer.

There may be extra weight in the front of the vehicle.

Cargo may fall out of the trailer.

Trailers are not made to be driven in reverse.

Backing is always dangerous because it is impossible to see everything that is behind your vehicle. Only drive in reverse if it is absolutely necessary.

3. When backing up while coupling a trailer, the tractor should be positioned:

Directly in front of the trailer.

Directly next to the trailer.

Parallel with the trailer.

When backing up to couple a trailer, you should position the tractor directly in front of the trailer. Trying to couple while backing at an angle could cause the trailer to move and the landing gear to break.

4. On a leaf spring:

Leaves should shift.

Leaves can be missing.

Leaves should not be broken.

When inspecting your vehicle's suspension, verify that leaf springs do not have missing or broken leaves. If at least one-fourth of the leaves in a leaf spring are missing, the vehicle will be put out-of-service until the defect is fixed.

5. Air tank drains:

Allow rain water to enter the tanks.

Are used to drain water and oil from the air tanks.

Should never be opened.

Must remain open while driving.

Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Manually operated air tank drains must be opened daily to remove this build-up.

6. The most common type of foundation brake used is the:

S-cam drum brake.

C-cam drum brake.

G-cam disc brake.

P-cam disc brake.

The most common type of foundation brake is an s-cam drum brake.

7. While inspecting coupling equipment before a trip, the air lines should not:

Be connected to the glad hands.

Have any slack.

Be secured.

Be leaking.

When inspecting the convertor dolly, ensure that all components are present and in proper working condition. Be sure to check the upper and lower fifth wheel, the air lines, and the electric lines. The air lines should be securely attached to the proper glad hands and should not contain any leaks. They should be attached with enough slack to allow easy turning.

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