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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. To make the brakes work, air brakes use:
hydraulic air.
compressed air.
2. When you double your speed, the braking distance is:
the same.
4 times longer.
3 times longer.
3. The trolley valve should be used only:
to prevent skids.
to test the trailer brakes.
in driving.
4. Air storage tanks:
use parts of the service brake systems to stop the vehicle in a brake system failure.
hold compressed air for the brakes.
pump air into the air storage tanks.
5. To prevent a rollover, the driver should:
make quick lane changes if possible.
drive slowly around corners, on ramps, and off ramps.
drive on the shoulder if possible.
6. When driving with more than one trailer, the _______ trailer should be the first one behind the tractor.
7. You are driving a modern truck with a manual transmission. When going down a hill you should usually:
use the same gear you would use to go up the hill.
shift into neutral and coast.
use a lower gear than would be required to go up the hill.
8. When more cargo is piled up in a truck, the center of gravity moves:
higher up from the road.
closer to the ground.
to the left side of the truck.
9. With low beams, drivers can see ahead about:
250 feet
15 feet
100 feet
10. When conducting a pre-trip inspection:
the inspection report should only be reviewed if you will be carrying passengers.
you should review the last vehicle inspection report.
the vehicle inspection report should not be reviewed unless your supervisor tells you to do so.
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Doubles Triples IA CDL Test

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