All your missed questions are saved
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It's a practice test that's automatically made up of all your missed questions. Once you finish this test, you’ll be able to revisit your Challenge Bank™ to practice and sharpen your skills.
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View All PlansTo 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.
Driver’s Ed is - nobody wants to set foot inside the DOT. That’s why millions of learners trust us for simple, visual, effective prep.
We are an officially recognized FMCSA Entry-Level Driver Training provider and a proud partner to over 2,500 libraries. We work with safety organizations like GHSA and the National Safety Council to help create safer roads for everyone.
Our trademarked system automatically saves questions you miss, creating personalized tests that target your weak spots until you’ve mastered the material.
Get smarter as you study. Our new AI-powered feedback provides detailed, question-level insights to help you understand the why behind each answer.
Go beyond the boring black-and-white manual. Our interactive handbook lets you read, listen with an MP3 audio version, or even chat with it to find the information you need, faster.
We build our practice questions from the current 2025 IA Driver Handbook and refine them using patterns recent test‑takers report.
Driver handbook • Knowledge‑test/permit overview • Fees & ID requirements • Office/appointment info
We mirror recurring themes (e.g., right‑of‑way traps, sign look‑alikes) and use similar distractors and wording styles.
We don’t collect or publish actual test items and we’re not affiliated with DOT.
