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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 Iowa doubles triples test consists of 20 questions. To pass, you must correctly answer at least 16 questions (80%). The IA CDL doubles triples test covers the following sections of the Iowa CDL Manual: Driving Safely, Air Brakes (if you plan to operate vehicles equipped with air brakes), Combination Vehicles, Doubles and Triples. Take this IA CDL practice test now to prepare for the actual test!
1. Under a pressurized system, the radiator cap:
should never be hot.
should be removed when the coolant is hot.
should never be removed until the system has cooled.
2. When preparing to make a right turn, you should NOT turn wide to the left as you start the turn. Why?
A following driver may try to pass you on the right.
Turning wide to the left can cause your vehicle to tilt.
It makes the turn harder.
3. To use the controlled braking method in an emergency, you should:
apply the brakes when the wheels lock up.
apply your brakes all the way, and release the brakes when the wheels lock up.
apply the brakes as hard as you can without locking the wheels.
4. When coupling double trailers, you can secure the second trailer by:
using the trailer spring brakes.
chocking the wheels.
All of the above.
5. To prevent getting sleepy while driving, you should:
keep cool by opening the window.
keep the cab warm.
drive alone whenever possible.
6. When driving a 60-foot truck at 50 mph, your minimum following distance should be:
7 seconds
6 seconds
5 seconds
7. When your vehicle starts to skid, you must take action to:
use controlled braking.
accelerate and countersteer.
restore traction to the tires.
8. Overloading a vehicle with cargo can have negative effects on all of the following except:
Weight limits
9. For safe handling, the heaviest trailer should be:
the second trailer in a triple.
the last trailer.
behind the tractor.
10. To avoid becoming an aggressive driver you should:
make gestures to other drivers.
give other drivers the benefit of the doubt.
give other drivers your full attention.
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IA 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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