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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 South Dakota doubles triples test consists of 20 questions. To pass, you must correctly answer at least 16 questions (80%). The SD CDL doubles triples test covers the following sections of the South Dakota CDL Manual: Driving Safely, Air Brakes (if you plan to operate vehicles equipped with air brakes), Combination Vehicles, Doubles and Triples. Take this SD CDL practice test now to prepare for the actual test! Important: Triple trailers are not legal in South Dakota.
1. What should you do if you doubt you have safe space to pass under a low bridge?
Go slowly, and take another route if you are not sure you can make it.
If no warnings are posted, assume there is enough clearance under the bridge and proceed slowly.
Assume that the height posted at the bridges is correct.
Increase the weight of your vehicle to clearing under the bridge.
2. Before driving a vehicle with a dual air system, allow time for the air compressor to build up a minimum of ____ pressure in both the primary and secondary systems.
50 psi
75 psi
100 psi
25 psi
3. If during vehicle inspection a tire is too hot to touch, you should:
let air out.
immediately decrease air pressure.
remain stopped until the tire cools off.
make sure there is enough engine oil on the tires.
4. Which of the the following statements about fatigue is true?
Fatigue impairs your vision and judgment.
Fatigued driving is one of the leading causes of accidents.
Fatigue may cause you to not see and react to hazards.
All of the above.
5. An item that is 15 feet long placed on a flatbed trailer should have at least:
2 tie-downs.
15 tie-downs.
1 tie-down.
3 tie-downs.
6. Alcohol:
improves muscle coordination.
impairs depth perception.
improves reaction time.
does not affect judgement.
7. If your vehicle thumps or vibrates heavily, it may be a sign that:
one of the tires has gone flat.
the brakes have failed.
the engine belt is loose.
you need to shift up.
8. Emergency brakes must be held on by:
air pressure.
dynamic pressure.
hydraulic pressure.
mechanical force.
9. For safe handling, the heaviest trailer should be:
behind the tractor.
the second trailer in a triple.
the last trailer.
None of the above.
10. If your brakes fail on a steep mountain downgrade, you should:
use an escape ramp if it is available.
change lanes after making sure there is enough room.
go right if the shoulder is clear.
leave the road immediately.
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SD CDL Doubles 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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