IA CDL Double/Triple Trailers Practice Test 2 2025
- Perfect for first-time and renewal CDL/CLP applicants, and those adding endorsements
To legally operate double or triple trailer combinations, you must pass the Double/Triple Trailers Knowledge Test, which adds the T Endorsement to your Class A CDL. You’ll find a wide variety of topics covered on the test, and standard study guides may not be your best option for preparing! The Iowa test includes 20 multiple-choice questions, and you must score 80% or higher (at least 16 correct answers) to pass. If you fail, the Iowa Department of Transportation (DOT) requires a one-business-day waiting period before retesting. Additional fees will apply if you fail the exam three times.
Our Free Iowa CDL Double/Triple Trailers Knowledge Practice Tests are designed to help you pass on your first try. They mimic the official Iowa exam format and include real-time feedback, hints, and AI learning tools to improve retention and speed learning.
Our practice questions were designed to align with the latest Iowa CDL Manual and cover safety concepts like gentle and steady steering to avoid the “crack-the-whip” effect, safe coupling and uncoupling procedures, preventing rollovers and jackknifing, proper braking and following distances, and inspections.
Obtaining your T Endorsement can unlock higher pay and better job opportunities in Iowa. With major roadways like I-80, I-35, and I-380, as well as hubs in Des Moines, Cedar Rapids, Davenport, and Council Bluffs, the state provides the infrastructure and demand for drivers certified with the T endorsement. Companies such as TMC Transportation, CRST, and Ruan Transportation frequently seek drivers with this endorsement.
To further your qualifications, we recommend you consider pursuing endorsements for Tank Vehicles (N), Hazardous Materials (H), the X Combo Endorsement, Passenger (P), and School Bus (S) drivers. Each endorsement requires a separate knowledge test, and we provide Iowa-specific practice tests for each one!
Because most double/triple trailer configurations use air brakes, you’ll need to pass the Air Brakes Knowledge Test and a skills test in a vehicle with air brakes to remove any “L” or “Z” air brake restrictions on your license. Can you already tell where we’re going next?! We offer dedicated Iowa Air Brakes Practice Tests to help you prepare!
This is Test Two in our Hawkeye State CDL Double/Triple Trailers suite. Be sure to explore our full range of Iowa practice tests, including those for air brakes, combination vehicles, tankers, hazardous materials, passengers, and school buses.
Verified for accuracy: October 2025
Reviewed by Steven Litvintchouk, M.S.
Chief Educational Researcher (ACES member)
Methodology & Editorial Policy
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