Florida CDL Doubles and Triples Practice Test 2026
The Doubles and Triples test adds the T endorsement, which you need to pull double or triple trailers on a Class A license. It covers Section 7 of the Florida CDL Handbook: pulling double and triple trailers safely, coupling and uncoupling them, inspecting them, and checking their air brakes.
The crack-the-whip effect, converter dollies, and the order you couple trailers in are the key topics.
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Question 1 of 15
Because backing doubles and triples is almost impossible to do safely, drivers should:
Doubles and triples jackknife and swing unpredictably when reversed, making safe control nearly impossible. If you must back into a spot, unhook the trailers and move each one separately by hand or with a dolly.
Handbook: 7.1 - Backing Doubles/Triples
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Question 2 of 15
Compared to a single trailer combination, doubles and triples are generally:
Each additional trailer adds more pivot points, which increases the chance of a rollover or jackknife. The rearmost trailer is especially prone to the "crack-the-whip" effect during turns or sudden moves.
Handbook: 7.1 - Pulling Doubles and Triples
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Question 3 of 15
After connecting the converter dolly air lines to the rear trailer, before backing under it you should:
Charging the dolly fills its air tanks with pressure. Disconnecting the emergency line after charging causes the dolly brakes to lock, so the rear trailer stays still and won't roll while you back the second trailer under it.
Handbook: 7.2 - Coupling Doubles
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Question 4 of 15
When uncoupling a rear trailer from a set of doubles, you should first:
Before disconnecting anything, you need to support the rear trailer so it doesn't drop or become unstable when the dolly is removed. Lowering the landing gear just enough to take some weight off the dolly keeps everything stable without lifting the trailer off the dolly's fifth wheel.
Handbook: 7.2 - Uncoupling Doubles
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Question 5 of 15
Older trailers with a 'three-line' (or three-valve) air brake system are:
Three-line systems were an older design that required a separate hand valve to operate the trailer brakes. This setup is no longer manufactured, but you may still encounter these trailers out on the road.
Handbook: 7.3 - Older Trailer Air Systems
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Question 6 of 15
When inspecting a converter dolly, which of the following should you check?
A converter dolly has its own unique parts that connect the trailers together, so each one must be checked individually. The drawbar eye, safety chains, and turntable handle the coupling, while tires, lights, and air lines are standard checks on any unit. The fifth wheel on the dolly is what the rear trailer actually sits on, so it must be properly greased and latched.
Handbook: 7.4 - Inspecting Doubles and Triples
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Question 7 of 15
For an air leakage test on a combination vehicle with the engine off and brakes applied, the air pressure should not drop more than:
With the engine off and the brakes applied, the limit is 3 psi in one minute for a single vehicle and 4 psi in one minute for a combination vehicle, no matter how many trailers are in it. If you thought a longer combination is allowed to leak more, that is the trap: extra trailers mean more connections to inspect, not a looser limit. See handbook 5.3.3.
Handbook: 5.3.3 - Test Air Leakage Rate
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Question 8 of 15
When pulling doubles or triples with trailers of different weights, the heaviest trailer should be:
The heaviest trailer is most stable when it's closest to the tractor, where the connection is strongest. Lighter trailers placed farther back are more prone to swaying and rocking, so putting heavy weight there increases the risk of a rollover or jackknife.
Handbook: 7.1 - Loading and Trailer Order
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Question 9 of 15
Off-tracking on doubles and triples means:
When a long vehicle turns, the rear wheels cut the corner and travel a shorter, tighter arc than the front wheels. This is called off-tracking, and it gets worse the more trailers you add. It means the rear of your vehicle swings closer to the curb or into adjacent lanes than the front does.
Handbook: 7.1 - Off-tracking
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Question 10 of 15
Wind affects doubles and triples more than most vehicles. In strong winds, you should:
Doubles and triples have large, tall surfaces that catch wind like a sail, making them much harder to control in strong gusts. Reducing speed lowers the force the wind exerts on the vehicle, giving you better control. If winds are severe enough that control becomes difficult, pulling off safely is the right call rather than risking a rollover or lane departure.
Handbook: 7.1 - Wind
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Question 11 of 15
The trailer air supply valve (sometimes red, octagonal) in the cab:
This valve controls the flow of air from the tractor to the trailer braking system. Closing it shuts off the air supply to the trailers and activates the tractor protection valve, which prevents the tractor from losing its own air if a trailer breaks away or develops a major air leak.
Handbook: 7.3 - Tractor Protection and Trailer Air Supply
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Question 12 of 15
Before driving a set of doubles or triples, the driver should pay special attention to:
Longer and heavier combinations face more restrictions than single trailers. Some bridges can't handle the extra weight, some overpasses are too low, and certain roads or states ban doubles and triples entirely. Check these restrictions before you leave, not after you're already on the road.
Handbook: 7.1 - Route Planning
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Question 13 of 15
The amber ABS malfunction lamp on a trailer is used to indicate:
The amber lamp on the trailer signals that the ABS on that trailer is not working properly. You should still have normal braking, but the antilock function may not prevent wheel lockup during a hard stop.
Handbook: 7.4 - ABS Indicator Lights
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Question 14 of 15
Before backing the tractor under the first semi-trailer of a double, you should prepare the setup:
Coupling a tractor to the first trailer of a double follows the same steps as a standard tractor-trailer hookup. Once that first combination is complete, you then pick up the second trailer using the dolly to complete the double.
Handbook: 7.2 - Coupling and Uncoupling Doubles
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Question 15 of 15
A driver should know that the rearmost trailer of a triple:
Each trailer in a combination magnifies the side-to-side motion from the one ahead of it. By the time that motion reaches the last trailer, it is much more severe than what the driver feels up front, making rollover a real danger during turns or sudden lane changes.
Handbook: 7.1 - Rollover and Crack-the-Whip
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Download on the App StoreMore Florida CDL practice tests
- General Knowledge Practice TestTaken by every CDL applicant, whatever the license class.
- Air Brakes Practice TestRequired if your vehicle has air brakes, including air over hydraulic.
- Combination Vehicles Practice TestRequired for a Class A license.
- Hazmat Practice TestH endorsement. Also needs a TSA background check.
- Passenger Practice TestP endorsement, for vehicles that carry 16 or more people.
- Tank Vehicles Practice TestN endorsement, for tanks over 119 gallons each and 1,000 combined.
- School Bus Practice TestS endorsement, for driving a school bus.
- Road Signs PracticeSigns, signals and pavement markings, as a refresher.
Florida CDL Exam is an independent study aid. It is not affiliated with, endorsed by, or approved by the FLHSMV, the FMCSA, or any Department of Transportation. Questions are original, written from the public Florida CDL Handbook, and are not actual exam questions. Read the official Florida CDL Handbook (PDF).