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Safely pulling double and triple trailers requires knowledge and skill. If you want to pull double or triple trailers, you must add the Doubles/Triples (T) endorsement to your Class A CDL. The Maryland doubles triples test consists of 20 questions. To pass, you must correctly answer at least 16 questions (80%). The MD CDL doubles triples test covers the following sections of the Maryland CDL Manual: Driving Safely, Air Brakes (if you plan to operate vehicles equipped with air brakes), Combination Vehicles, Doubles and Triples. Take this MD CDL practice test now to prepare for the actual test!
1. Combination vehicles usually:
require more driving skill than single CMVs.
are shorter than single than single CMVs.
are easier to drive than single than single CMVs.
All of the above.
2. When transporting cargo, cargo securement must be checked within the first _____ miles of a trip and every _____ miles after.
100; 150
150; 250
50; 250
50; 150
3. A trailer jackknife is more likely to happen when the trailer is:
loaded to its full capacity.
None of the above.
4. The tractor protection valve:
controls the emergency brakes on combination vehicles.
supplies air to the trailer air tanks.
works the trailer brakes.
keeps air in the tractor brake system should the trailer break away or develop a bad leak.
5. Weight that is loaded so there is a high center of gravity:
causes greater chance of rollover.
makes a vehicle easier to handle.
reduces the chance that the load will shift to the side or fall off.
All of the above.
6. By pushing the trailer air supply control knob in, you:
supply the tires with air.
supply the trailer with air.
shut the air off and put on the trailer emergency brakes.
keeps air in the tractor or truck brake system.
7. If the engine catches fire, you should:
turn off the engine as soon as you can.
avoid shooting foam from the vehicle's underside.
open the hood as soon as you can.
pull into a service station and notify the emergency services.
8. In a combination vehicle, ________ is most likely to turn over.
the last trailer
the trailer behind the tractor
the tractor
All of the above.
9. To make the brakes work, air brakes use:
compressed air.
hydraulic air.
carbon monoxide.
10. You are driving a double. Before entering traffic, you should:
turn on your headlights.
assume there is enough room to merge into traffic.
always come to a complete stop.
make sure you have a large enough gap before entering or crossing traffic.
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MD CDL Doubles Test

Number of questions: 20
Correct answers to pass:16
Passing score:80%
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