Florida CDL Combination Vehicles Practice Test 2026
The Combination Vehicles test is required to drive a tractor-trailer or any other combination, which means anyone going for a Class A license. It covers Section 6 of the Florida CDL Handbook: driving combinations safely, combination air brakes, antilock brakes, coupling and uncoupling, and the extra inspection items.
Rollover risk, off-tracking, the trailer hand valve and the tractor protection valve are the topics that trip people up most. Each answer below shows the reason and the handbook section.
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Question 1 of 15
A drive-wheel skid in a tractor-trailer is most likely to cause:
When drive wheels lock up and lose traction, the rear of the tractor pushes forward with nothing to grip the road. This causes the trailer to push the tractor sideways, swinging the cab around. The classic jackknife position.
Handbook: 6.1 - Driving Combination Vehicles Safely
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Question 2 of 15
After connecting the air lines to the trailer but before backing under, you should:
Supplying air to the trailer charges the brake system, and then pulling out the trailer air supply knob applies the trailer brakes so the trailer won't roll while you back under it.
Handbook: 6.4 - Coupling and Uncoupling
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Question 3 of 15
For a combination vehicle air brake leak test with the service brakes applied, what is the maximum allowable air loss?
With the service brakes held down, a combination vehicle should lose no more than 4 psi per minute. A higher leak rate means the brakes may not hold under sustained pressure, which is especially dangerous when hauling a loaded trailer.
Handbook: 6.2 - Combination Vehicle Air Brakes
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Question 4 of 15
When inspecting the coupling area on a combination vehicle, you should check all of the following EXCEPT:
The license plate is not part of the coupling system. During a coupling inspection, you focus on mechanical connection points, things like the fifth wheel, kingpin, safety chains, and glad hands, to make sure the trailer is securely attached.
Handbook: 6.5 - Inspecting a Combination Vehicle
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Question 5 of 15
On a Florida Class A CDL, what does an O restriction mean?
The "O" restriction means the driver passed their skills test using a pintle hook or other non-fifth-wheel coupling instead of a standard fifth wheel. Because they were never tested on a fifth-wheel connection, they are not licensed to drive a combination that uses one.
Handbook: 1.4 - Other CDL Rules
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Question 6 of 15
Bobtail tractors (tractors without a trailer) generally have:
A bobtail looks light, so drivers expect it to stop fast. Tests show the opposite: without a loaded trailer pressing down on the drive axle, the brakes get poor traction and the wheels lock easily, so a bobtail takes longer to stop than a tractor-semitrailer loaded to maximum gross weight.
Handbook: 6.1 - Driving Combination Vehicles Safely
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Question 7 of 15
A sliding fifth wheel allows the driver to:
Sliding the fifth wheel forward or backward shifts how much of the trailer's weight rests on the steer axle versus the drive axles. This lets you balance the load to stay within legal axle weight limits.
Handbook: 6.4 - Coupling and Uncoupling
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Question 8 of 15
What happens to the trailer brakes if the air supply from the tractor is lost?
Trailers have spring brakes that are held open by air pressure. If the air supply from the tractor is cut off or lost, that pressure drops and the spring brakes automatically clamp down, bringing the trailer to a stop.
Handbook: 6.2 - Combination Vehicle Air Brakes
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Question 9 of 15
An amber (yellow) light labeled ABS on the trailer or on the dash of a newer combination indicates:
The amber ABS warning light means the anti-lock braking system has a fault, but the base brakes still function normally. You can continue driving, but the ABS may not prevent wheel lockup during hard braking until the problem is repaired.
Handbook: 6.5 - Inspecting a Combination Vehicle
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Question 10 of 15
Trailer fishtailing or swing on a slippery road is typically the result of:
When trailer wheels lose grip, usually because the brakes lock up or the trailer's momentum pushes it sideways, the rear of the trailer swings out to the side. This is called fishtailing, and it gets worse if you try to steer out of it without first releasing brake pressure to let the wheels roll again.
Handbook: 6.1 - Driving Combination Vehicles Safely
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Question 11 of 15
During the tug test, if the tractor pulls away from the trailer, it means:
If the tractor moves forward but the trailer stays put, the fifth-wheel jaws never locked around the kingpin. A proper coupling holds the two units together as one. Any separation during the tug test means you must stop and recouple before driving.
Handbook: 6.4 - Coupling and Uncoupling
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Question 12 of 15
A driver should NOT use the trailer hand valve to prevent a jackknife because:
Using the hand valve locks up only the trailer wheels, which causes the trailer to skid sideways. Exactly what leads to a jackknife. The foot brake pedal applies all the brakes together, which is much safer on slippery roads.
Handbook: 6.2 - Combination Vehicle Air Brakes
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Question 13 of 15
Cargo on a trailer must be secured so that it:
Cargo that shifts, falls, or leaks can throw off your vehicle's balance, spill onto the road, or injure people. Securing it against emergency braking and sudden steering covers the most extreme forces the load will experience during a normal trip.
Handbook: 6.5 - Inspecting a Combination Vehicle
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Question 14 of 15
If you start to jackknife or skid, the first correct action is usually to:
Locking the wheels causes skids. Releasing the brakes lets the wheels spin again, which restores traction and gives you steering control back. Once the wheels are rolling, you can steer (countersteer) to straighten the vehicle.
Handbook: 6.1 - Driving Combination Vehicles Safely
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Question 15 of 15
Before connecting the air lines, you should:
Dirt or damaged seals on the glad hands can cause air leaks, which reduces braking ability. Inspecting and cleaning the couplers before connecting ensures a proper seal and a reliable air supply to the trailer brakes.
Handbook: 6.4 - Coupling and Uncoupling
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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.
- 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.
- Doubles and Triples Practice TestT endorsement, for pulling double or triple trailers.
- 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).