Question 1 of 20
When uncoupling, you should lower the landing gear:
Correct. Lower the landing gear and snug it against the ground before releasing the fifth-wheel jaws so the trailer doesn't drop when you pull away.
Mississippi Combination Vehicles CDL Practice Test
This is a free 20-question practice test for the Combination Vehicles portion of the Mississippi Commercial Driver's License knowledge exam. Questions are pulled from a pool of 55 drawn from the AAMVA CDL Manual, which is the source document the Mississippi Department of Public Safety Driver Service Bureau uses to write its actual exam.
How it works: Click an answer. The correct choice highlights in green, and you'll see a short explanation. Aim for 85% or better before you sit for the real test in Mississippi.
Question 2 of 20
Your trailer ABS warning lamp is on. The trailer service brakes:
Correct. Trailer service brakes still work normally without ABS. Have the system repaired; ABS gives extra control during emergency braking.
Question 3 of 20
Maximum allowable trailer-brake leakage rate (engine off, brakes released, combination vehicle) is:
Correct. Combination vehicles: no more than 3 psi/min with brakes released, 4 psi/min with brakes applied.
Question 4 of 20
A sliding-tandem trailer allows you to:
Correct. Sliding tandems shift trailer axles forward (more weight on tractor) or aft (more weight on trailer axles), helping meet axle-weight limits.
Question 5 of 20
If the trailer is too low for coupling, you should:
Correct. Use the landing gear hand crank to raise the trailer to the proper height (just below fifth-wheel level) before backing under.
Question 6 of 20
Off-tracking refers to:
Correct. Off-tracking is the tendency for trailer wheels to follow a smaller-radius path than the tractor wheels through a turn, more pronounced with longer wheelbases.
Question 7 of 20
When inspecting the kingpin during pre-trip, look for:
Correct. A worn, cracked, or bent kingpin can fail under load. The locking jaws must close completely around the shank, not just the head.
Question 8 of 20
Length and weight increase what about a combination vehicle?
Correct. Longer, heavier rigs need more stopping distance, swing wider in turns, have larger blind spots, and require more time and space to change lanes.
Question 9 of 20
Auxiliary equipment (refrigeration, hydraulic lift gates) on the trailer:
Correct. Reefer units, lift gates, and other auxiliary equipment add weight and may shift CG. Inspect securement and check operation in pre-trip.
Question 10 of 20
To make a trailer go where you want when backing, the steering wheel should:
Correct. Backing is opposite-direction steering: to swing the trailer right, turn the wheel left first, then correct as the trailer follows.
Question 11 of 20
A combination vehicle on slippery roads should be driven:
Correct. Reduce speed by at least one third on wet roads and one half on snow; double following distance on slick surfaces.
Question 12 of 20
When you "G.O.A.L." in trucking, you:
Correct. G.O.A.L. — Get Out And Look — is the universal driver-school rule before any tight backing maneuver.
Question 13 of 20
To recover from a trailer skid, you should:
Correct. Release the brakes so the trailer wheels can rotate again and re-establish traction. Continued braking will worsen the skid.
Question 14 of 20
Before uncoupling, you should:
Correct. Proper sequence: park level, lower landing gear to support the trailer, disconnect lines, release jaws, then pull forward slowly. Skipping any step risks dropping the trailer.
Question 15 of 20
A "trailer skid" happens when:
Correct. When trailer wheels lose traction (often from over-application of trailer brakes alone), the trailer can slide sideways — a trailer skid or trailer swing.
Question 16 of 20
Combination vehicles are usually:
Correct. Combination vehicles (tractor-trailer rigs) are heavier, longer, and articulate at the fifth wheel — all making them more demanding than single-unit trucks.
Question 17 of 20
When you connect the glad-hands, you should:
Correct. Push the glad-hands together so the rubber seals match, then rotate to lock. Be sure red goes to red and blue goes to blue (the lines themselves often cross to keep colors matched).
Question 18 of 20
On a tight curve or exit ramp, a tractor-trailer is most likely to roll over because:
Correct. Centripetal forces in a curve push the cargo outward; a high center of gravity multiplies the tipping moment. Slow before the curve.
Question 19 of 20
A high-mounted trailer kingpin is dangerous because:
Correct. If the trailer is too high, the fifth wheel slides under without the kingpin engaging the locking jaws. The trailer is not coupled and can drop when you pull away.
Question 20 of 20
A safe practice when arriving at a destination is to:
Correct. Slow approach with mirror checks gives time to identify clearance issues and pedestrians.
About the Mississippi Combination Vehicles exam
Most states administer 20 Combination Vehicles questions and require 80% to pass. The exam emphasizes the unique handling of articulated vehicles: how trailers track behind the tractor, how to prevent rollover, how to manage rearward amplification with multi-trailer combinations, and the correct sequence to couple and uncouple.
The Mississippi Department of Public Safety Driver Service Bureau follows the federal CDL standards established by FMCSA. To earn the Combination Vehicles credential, you must answer at least 80% of the questions correctly. Many candidates score lower the first time because the test pulls from a large pool — refreshing this page will give you a different mix of questions, drawn from the same authoritative source.
Want more practice? Try the full Combination Vehicles question bank or browse all Mississippi CDL practice tests.