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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. Enough tread is especially important in winter conditions. You need at least ________ tread depth on steering axle tires.
2/8 inch
4/32 inch
6/24 inch
2. Air pressure should build up in a single air system, within about:
3 minutes.
10 minutes.
15 minutes.
3. It may not be safe to operate at legal maximum weights:
on two-way streets.
in hot weather.
during bad weather or in mountains.
4. If you are caught in strong winds, you should:
speed up while keeping a strong grip on the steering wheel.
immediately take your foot off the accelerator.
keep a strong grip on the steering wheel and slow down or pull off the roadway.
5. Which of the following is a good way to avoid becoming an aggressive driver?
Keep your following distance reasonable.
Be realistic about your travel time.
All of the above.
6. It's very important to distribute the cargo so it is:
as high up as possible.
in the centre of the load.
as low as possible.
7. Combination vehicles have __ air lines.
8. If driving a heavy vehicle, you should:
try to pass other vehicles going uphill.
stay in the right lane.
stay in the left lane.
9. The posted speed for a curve that may be safe for a straight truck:
is likely to be safe for a double or triple.
could be too fast for a double or triple.
can be ignored when driving a double or triple.
10. Pre-trip inspections of doubles and triples should:
be done by the shipper.
take less time than inspecting straight trucks.
take more time than inspecting straight trucks.
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IA CDL Doubles Triples Test

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