Pennsylvania Combination Vehicles CDL Practice Test
Below are 25 exam-style questions for the Pennsylvania Combination Vehicles CDL knowledge test, modeled on the FMCSA-aligned content used by the Pennsylvania Department of Transportation. 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 Sends supply air to the trailer reservoirs
- B Drains the trailer reservoir
- C Sends air pressure to apply trailer service brakes
- D Carries electrical power
- A Fuel
- B Electrical power for trailer lights and ABS
- C Air for the brakes
- D Hydraulic fluid
- A Lose engine power
- B Roll over before sliding
- C Stop suddenly
- D Spin out
- A Smoke from the cab
- B Steering wander only
- C Engine knocking
- D Pulling, sticking, or unusual feel as you apply the brakes
- A The tractor brakes lock up
- B The fifth wheel breaks
- C The trailer brakes lock up
- D A wheel bearing fails
- A Asking a mechanic
- B Pressing the pedal once at startup
- C Listening to the brake light
- D Performing the seven-step air-brake check before each trip
- A Stops only with parking brake
- B May actually take longer to stop because brakes are designed for the loaded weight
- C Stops faster than when loaded
- D Stops in the same distance
- A Honk the horn
- B Tug the trailer with the trailer parking brakes set
- C Listen for a click
- D Look at the locking jaws only
- A Can be detected during pre-trip inspection by visual and pressure checks
- B Show up only at high speed
- C Need a mechanic to find
- D Are caused by low fuel
- A Apply the trailer hand valve harder
- B Release the brakes to allow the trailer wheels to roll again, then steer
- C Disconnect the air supply
- D Accelerate
- A Every 3 hours
- B Before, during, and after coupling
- C Only at the destination
- D Only at the start of the day
- A Leave the gear up
- B Use blocks instead
- C Lower the landing gear all the way until firmly on the ground, then a few extra cranks
- D Raise the gear partway
- A A vehicle length
- B One second per 10 feet of vehicle length below 40 mph, plus one extra second above 40 mph
- C No specific rule
- D Two car lengths
- A It is illegal in some states
- B It can damage the cab and the trailer (cab corner crush)
- C It is the standard procedure
- D It is fine if you are careful
- A Be in the low position when traveling
- B Be in the stowed (high) position when traveling
- C Be locked at half-height
- D Be removed
- A Connect only air; electrical is optional
- B Connect any line first; order doesn't matter
- C Connect air emergency line first, then service line, then electrical (or per company policy) — verify with brake check
- D Connect electrical first, then air
- A The drive wheels lose traction and the tractor begins to slide
- B The trailer is too heavy
- C The tractor parking brake fails
- D The fifth wheel disengages
- A Failure to grease
- B Coupling with the trailer too high
- C All of the above
- D Backing too fast
- A A height that requires the tractor to drop down to fit
- B Whatever height it happens to be
- C Maximum legal height
- D A height where the tractor will lift the trailer slightly when backing under
- A Stop on the tracks if traffic ahead slows
- B Shift in the middle of the track
- C Cross in a low gear without shifting
- D Honk and accelerate
- A By the trailer hand valve
- B By pushing in the red trailer-air-supply valve
- C By pulling out the red trailer-air-supply valve
- D By setting the red trailer-air-supply valve
- A It uses air brakes
- B Its center of gravity is high
- C Its tires are wider
- D It is shorter than a straight truck
- A Is part of the tractor
- B Is used to convert a semitrailer into a full trailer for towing in combination
- C Is used only when triple-towing
- D Replaces the fifth wheel on the tractor
- A Air leakage in the supply line, low pressure, or a brake-balance issue
- B Cargo placement
- C Driver fatigue
- D Engine wear
- A Triangular, green, marked SERVICE
- B Square, white, marked CHARGE
- C Round, blue, marked TRACTOR
- D Octagonal, red, marked TRAILER AIR SUPPLY
Study tips for the Pennsylvania Combination Vehicles exam
The Combination Vehicles portion of the Pennsylvania CDL exam is graded out of the bank of questions the Pennsylvania Department of Transportation draws from each year. While the exact bank is not published, every question is sourced from the Combination Vehicles chapter of the Pennsylvania 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 Pennsylvania 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 Pennsylvania Department of Transportation 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 Pennsylvania 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 Pennsylvania 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 Pennsylvania Department of Transportation office.
Already comfortable with this endorsement? Drill another: PA General Knowledge · PA Air Brakes · PA Hazardous Materials · PA Passenger · PA School Bus · PA Tank Vehicle · PA Doubles / Triples
New to the CDL process in Pennsylvania? Read How to apply for a CDL in Pennsylvania for the document checklist and step-by-step timeline.