Combination

All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Maryland Commercial Driver License.. Read More

All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Maryland Commercial Driver License Manual. Section 6 provides the information needed to safely operate tractor-trailers, doubles, triples, and straight trucks with trailers. The test is made up of 20 multiple-choice and true/false questions, and applicants will need to correctly answer a minimum of 16 questions to pass. The Combination test is not a replacement for the Double/Triple endorsement test.

Number of Question
Passing Score

8. To help prevent rollovers, you should:

Explanation
To lower the risk of a rollover, load your cargo as closely to the ground as possible. To further reduce this risk, take curves and corners slowly.

9. Trailers with low underneath clearance may be difficult to drive:

Explanation
Railroad-highway crossings may be difficult to cross when pulling a trailer with a low underneath clearance. In particular, both low-slung units and single-axle tractors pulling long trailers are especially challenging to drive over raised crossings.

10. A loss of air pressure in the emergency line will cause:

Explanation
The tractor protection valve keeps air in the trailer's braking system should the trailer break away or develop a leak. A loss of air pressure in the emergency line will cause the tractor protection valve to open and the emergency trailer brakes to activate.

11. When backing a trailer, you must first turn the steering wheel:

Explanation
When backing a vehicle without a trailer, a driver must turn the vehicle in the direction that they want to go. However, when backing with a trailer, the driver must begin by turning in the opposite direction. Once the trailer starts to turn, they should turn the wheel in the other direction to follow the trailer.

12. The emergency air line supplies air to the:

Explanation
The emergency air line (also known as the supply line) has two functions. The first is to supply air to the trailer air tanks, and the second is to control the emergency brakes on combination vehicles.

13. If a load is placed on one side of a trailer, the trailer:

Explanation
If the weight of a load is placed primarily one side of a trailer, the trailer may lean, increasing the risk of a rollover.

14. What is the tractor protection valve?

Explanation
A tractor protection valve keeps air in a tractor or truck air brake system should the trailer break away or develop a bad leak. The valve will close automatically if the pressure drops to an unsafe level.
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