Mississippi Combination Vehicles CDL Practice Test
Below are 25 exam-style questions for the Mississippi Combination Vehicles CDL knowledge test, modeled on the FMCSA-aligned content used by the Mississippi Department of Public Safety. Try to answer each question on your own before reading the answer key directly under it. The questions and answer choices are shuffled deterministically per state and endorsement, so the order will stay the same on repeat visits — that lets you genuinely measure your improvement.
- A Rust on the cab
- B The trailer to come uncoupled
- C Engine damage
- D Tire wear only
- A A separate compressor
- B Sensors at each wheel that release brake pressure when wheel lockup is detected
- C Hydraulic brakes
- D Hand valves
- A Two car lengths
- B A vehicle length
- C One second per 10 feet of vehicle length below 40 mph, plus one extra second above 40 mph
- D No specific rule
- A Released and visible after coupling
- B Tied with rope
- C Removed before driving
- D Locked and the safety latch in place after coupling
- A Backing too fast
- B Failure to grease
- C Coupling with the trailer too high
- D All of the above
- A Always halfway extended
- B Disconnected before driving
- C Lowered to the ground while driving
- D Fully raised before driving
- A Its tires are wider
- B It is shorter than a straight truck
- C It uses air brakes
- D Its center of gravity is high
- A Steering wander only
- B Smoke from the cab
- C Pulling, sticking, or unusual feel as you apply the brakes
- D Engine knocking
- A Are normal until the lining is gone
- B Should be replaced when worn beyond manufacturer specs
- C Only need attention every 5 years
- D Make the truck quieter
- A The trailer is too heavy
- B The drive wheels lose traction and the tractor begins to slide
- C The tractor parking brake fails
- D The fifth wheel disengages
- A Cargo placement
- B Driver fatigue
- C Air leakage in the supply line, low pressure, or a brake-balance issue
- D Engine wear
- A Both for parking and to prevent jackknife
- B Hold the vehicle when parking
- C Apply trailer brakes momentarily
- D Test the trailer brakes
- A Nothing will happen
- B The horn will sound
- C You will notice immediately because trailer brakes will not work properly
- D The trailer brakes will be locked on
- A Fuel
- B Air for the brakes
- C Hydraulic fluid
- D Electrical power for trailer lights and ABS
- A Loose or missing fifth-wheel mounting bolts
- B All of the above
- C Cracks in the kingpin
- D Misalignment between tractor and trailer
- A Trailer wheels lock more often than drive wheels in panic stops
- B ABS prevents jackknife in all cases
- C Brake balance is irrelevant
- D Drive wheels never lock
- A Cargo placement
- B The fuel mileage
- C Lane positioning at intersections
- D The trailer following the same path as the tractor in a straight line
- A Use the trailer hand valve
- B Set only the tractor parking brake
- C Set both tractor and trailer parking brakes
- D Leave the engine running with the brakes off
- A Sends supply air to the trailer reservoirs and controls the trailer emergency brakes
- B Operates the parking brake only
- C Drains the wet tank
- D Carries electrical signals
- A Only at the start of the day
- B Only at the destination
- C Every 3 hours
- D Before, during, and after coupling
- A Are caused by low fuel
- B Show up only at high speed
- C Can be detected during pre-trip inspection by visual and pressure checks
- D Need a mechanic to find
- A Tug the trailer with the trailer parking brakes set
- B Listen for a click
- C Honk the horn
- D Look at the locking jaws only
- A The trailer brakes lock up
- B A wheel bearing fails
- C The tractor brakes lock up
- D The fifth wheel breaks
- A Be in the low position when traveling
- B Be locked at half-height
- C Be in the stowed (high) position when traveling
- D Be removed
- A Loss of brake pressure
- B No effect
- C Small trailer movement
- D Large trailer angle changes; small inputs are key
Study tips for the Mississippi Combination Vehicles exam
The Combination Vehicles portion of the Mississippi CDL exam is graded out of the bank of questions the Mississippi Department of Public Safety draws from each year. While the exact bank is not published, every question is sourced from the Combination Vehicles chapter of the Mississippi CDL handbook, which itself is derived from the FMCSA Model Commercial Driver's License Manual. That means studying our practice tests, reading the corresponding handbook chapter, and re-reading the parts you got wrong is genuinely the most efficient route to a first-time pass.
Most successful applicants follow a simple cycle: take the practice test cold, write down every question you missed, open the matching chapter of the official Mississippi handbook, re-read the section that contains the right answer, then re-take the practice test 24 to 48 hours later. The 24-hour delay matters — sleep is when your brain commits new information to long-term memory, and CDL knowledge questions reward that kind of consolidated learning rather than cramming.
Pay particular attention to questions that include qualifier words like always, never, only, primary, or most. CDL test writers love to flip the right answer with a single qualifier. When two answer choices look almost identical, pay attention to the verb (is it must, should, or may?) and to any numbers (14 days, 100 air miles, 8 hours, 70/8 split). On endorsement tests in particular, watch for trick framing where a true statement about a different endorsement is offered as the "correct" answer to a question that is actually about Combination Vehicles.
Test-day logistics matter too. Bring photo ID, your Social Security card or birth certificate, your medical examiner's certificate (DOT card), and proof of state residency if you haven't already submitted those documents. The Mississippi Department of Public Safety will not let you sit for the knowledge exam without your documentation, and most offices charge an additional fee for re-attempts. Arrive early — the wait at most CDL testing offices runs 30 to 60 minutes — and silence your phone before the exam begins.
Finally, keep your General Knowledge fundamentals sharp even when you're focused on the Combination Vehicles exam. Many states administer multiple knowledge tests in a single sitting, and questions on weight definitions (GVWR, GCWR, GAWR), stopping distance, and the pre-trip inspection routine show up across endorsements. If you're unsure on the basics, sit a fresh Mississippi General Knowledge practice test before scheduling the real exam.
Next steps
Missed more than four questions? Re-read the Combination Vehicles study guide and the matching chapter in the official Mississippi CDL handbook. Then come back and re-take the test. Once you can score 22 of 25 or higher on three runs in a row, you're in good shape to schedule the real exam at your local Mississippi Department of Public Safety office.
Already comfortable with this endorsement? Drill another: MS General Knowledge · MS Air Brakes · MS Hazardous Materials · MS Passenger · MS School Bus · MS Tank Vehicle · MS Doubles / Triples
New to the CDL process in Mississippi? Read How to apply for a CDL in Mississippi for the document checklist and step-by-step timeline.