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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 Mississippi doubles triples test consists of 20 questions. To pass, you must correctly answer at least 16 questions (80%). The MS CDL doubles triples test covers the following sections of the Mississippi CDL Manual: Driving Safely, Air Brakes (if you plan to operate vehicles equipped with air brakes), Combination Vehicles, Doubles and Triples. Take this MS CDL practice test now to prepare for the actual test!
1. In a dual air brake system, if one air system is very low on pressure:
either the front or rear brakes will not be operating fully.
you should pump the brakes to restore pressure.
you should drive and brake as you always have.
the effect won't be noticeable for the first 50 miles.
2. In a combination vehicle, ________ is most likely to turn over.
the trailer behind the tractor
the tractor
the last trailer
All of the above.
3. It is safer to drive over (rather than to avoid) which of the following?
Paper and cloth sacks
Cardboard boxes
Plastic containers
None of the above.
4. Emergency brakes are:
required on all vehicles.
not required on doubles.
not required on buses.
not required on commercial vehicles with air brakes.
5. If your brakes fail on a steep mountain downgrade, you should:
stay on the road and keep looking for the next available escape ramp.
set the parking brake and park in an open area.
decide what to do as soon as you know your brakes do not work.
slow down until your vehicle comes to a complete stop.
6. Emergency brakes must be held on by:
air pressure.
mechanical force.
dynamic pressure.
hydraulic pressure.
7. Enough tread is especially important in winter conditions. You need at least ________ tread depth on steering axle tires.
2/8 inch
6/24 inch
4/32 inch
8/32 inch
8. When driving with cargo, you should re-check the cargo and securing devices as often as necessary to keep the load secure, and inspect again:
every 3 hours or 150 miles.
every day.
every 30 minutes or 50 miles.
every 6 hours or 300 miles.
9. Most heavy-duty vehicles use:
pressure brakes.
solid brakes.
hydraulic brakes.
air brakes.
10. The trailer hand valve should be used:
to check that the trailer emergency brakes are on.
to test the trailer brakes.
to check that the fire extinguisher is charged.
to check that the trailer is locked onto the tractor.
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MS CDL Doubles Triples Test

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