Iowa Tank Vehicle CDL Practice Test
Below are 25 exam-style questions for the Iowa Tank Vehicle CDL knowledge test, modeled on the FMCSA-aligned content used by the Iowa 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 In neutral
- B At posted speed
- C At least 5 mph below the posted curve speed when loaded
- D Above posted speed
- A Be especially careful with starts and stops because surge will be severe
- B Use only the parking brake
- C Drive normally
- D Skip the brake check
- A Cause rollover
- B Cause loss of control
- C All of the above
- D Push the vehicle through an intersection
- A Has more surge than a full or empty tank
- B Has less surge than a full tank
- C Has the same surge
- D Has no surge
- A All of the above
- B Stopping or starting in traffic
- C The tank is partially loaded and surge is highest
- D On curves, ramps, and slick surfaces
- A Baffled tanks
- B Compartmented tanks
- C Smooth-bore (unbaffled) tanks
- D Empty tanks
- A Bond and ground before opening the manhole
- B Disconnect the bonding mid-loading
- C Bond only after the loading is complete
- D Skip the bonding if the load is small
- A In low-speed maneuvers
- B On straight roads
- C In stopped traffic
- D On a curve or off-ramp at speeds the driver thought were safe
- A Disregard surge
- B Skip outage
- C All of the above
- D Use the trailer hand valve as a parking brake
- A Sharp and quick
- B At any speed
- C Smooth and gradual to minimize side-to-side surge
- D Without signaling
- A Check fittings and covers for leaks before leaving the loading site
- B Drive immediately
- C Allow the shipper to drive
- D Skip the inspection
- A Use parking brake intermittently
- B Be in low gear and use steady moderate brake application
- C Coast in neutral
- D Increase speed
- A It carries any liquid
- B It is a flatbed
- C It has a tank with rated capacity of 1,000 gallons or more (single tank or aggregate of portable tanks)
- D It carries dry cargo
- A Is illegal in the U.S.
- B Is divided into separate compartments
- C Has no internal structure
- D Has internal walls with holes that slow liquid movement
- A Increase speed
- B Use the escape ramp
- C Coast in neutral
- D Maintain pressure on the brakes
- A Skip the safety check
- B Mix freely
- C Allow the receiver to add chemicals
- D Verify product compatibility and follow safety procedures
- A Drive faster to limit the spill
- B Stop, isolate the area, and notify emergency services and the carrier
- C Allow product to leak until empty
- D Continue to the destination
- A Increase speed to clear the descent
- B Use the parking brake harder
- C Coast in neutral
- D Look for an escape ramp
- A Anywhere outside the cab
- B 25 feet of the vehicle
- C 10 feet of the vehicle
- D 100 feet
- A Release the wheel
- B Hold the steering wheel firmly because the load may push you forward
- C Apply the parking brake immediately
- D Disengage the clutch
- A Skip the venting
- B Open vents only after pressure is equalized
- C Drive while unloading
- D Open vents while pressure is high
- A Prevent static-electricity sparks during loading and unloading
- B Improve fuel mileage
- C Reduce noise
- D Prevent corrosion
- A There is no effect
- B Surge is severe
- C The vehicle is heavy and stops slower; surge is reduced but mass is high
- D It stops faster
- A Continue to the destination
- B Drive faster
- C Try to repair the leak yourself
- D Stop in a safe location, isolate the area, and notify the carrier and authorities
- A Set both parking brakes and chock the wheels if necessary
- B Leave the truck in gear without brakes
- C Park on the shoulder without securing
- D Use the trailer hand valve
Study tips for the Iowa Tank Vehicle exam
The Tank Vehicle portion of the Iowa CDL exam is graded out of the bank of questions the Iowa Department of Transportation draws from each year. While the exact bank is not published, every question is sourced from the Tank Vehicle chapter of the Iowa 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 Iowa 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 Tank Vehicle.
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 Iowa 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 Tank Vehicle 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 Iowa General Knowledge practice test before scheduling the real exam.
Next steps
Missed more than four questions? Re-read the Tank Vehicle study guide and the matching chapter in the official Iowa 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 Iowa Department of Transportation office.
Already comfortable with this endorsement? Drill another: IA General Knowledge · IA Air Brakes · IA Combination Vehicles · IA Hazardous Materials · IA Passenger · IA School Bus · IA Doubles / Triples
New to the CDL process in Iowa? Read How to apply for a CDL in Iowa for the document checklist and step-by-step timeline.