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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 Colorado doubles triples test consists of 20 questions. To pass, you must correctly answer at least 16 questions (80%). The CO CDL doubles triples test covers the following sections of the Colorado CDL Manual: Driving Safely, Air Brakes (if you plan to operate vehicles equipped with air brakes), Combination Vehicles, Doubles and Triples. Take this CO CDL practice test now to prepare for the actual test! Important: Triple trailers are not legal in Colorado.
1. For safe handling, the heaviest trailer should be:
the last trailer.
the second trailer in a triple.
behind the tractor.
None of the above.
2. Headache racks:
help you keep weights within legal limits.
protect you from being hit by your cargo.
can blind other drivers.
None of the above.
3. On any upgrade, gravity:
speed you up.
slows you down.
doubles your speed.
doesn't affect your speed.
4. To start moving without rolling back, you should:
partly engage the clutch before you take your right foot off the brake.
apply the trailer brake hand valve.
put on the parking brake whenever necessary.
All of the above.
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.
slow down until your vehicle comes to a complete stop.
set the parking brake and park in an open area.
decide what to do as soon as you know your brakes do not work.
6. Which of the following statements is true?
There is no way that short circuits due to damaged insulation can cause a vehicle fire.
Carrying a properly charged and rated fire extinguisher will help prevent fires.
Poor cargo ventilation is a common cause of fire.
Under-inflated tires will NOT cause a vehicle fire.
7. Driving in very hot weather:
can make it difficult to stay in your lane.
should never be done.
can increase tire pressure.
can decrease oil pressure.
8. You must have at least _____ inch tread depth in every major groove on front tires.
9. You should do an after-trip inspection:
once a month.
after each trip.
at least once a week.
after each stop.
10. Engine oil pressure should come up to normal within _________ after the engine is started.
two minutes
five minutes
ten minutes
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CO CDL Doubles Triples Test

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