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You can gain access to numerous driving opportunities by removing the air brakes restriction “L” from your Iowa Commercial Driver’s License (CDL). From Sioux City to Davenport, commercial truck lines and public transportation providers need drivers qualified to operate air-brake-equipped vehicles. Most semi-trucks, tractor-trailers, and full-size buses are equipped with these systems. Air brakes are necessary to allow drivers to regulate their speed while transporting large amounts of weight. This ability is critical for navigating your way around sharp turns and coming to a complete stop in heavily congested traffic. The presence of the “L” restriction on your CDL limits your employment options, but you have the option of removing it to pursue greater driving opportunities. However, you should make sure to receive comprehensive training, allowing you to exhibit extensive knowledge of air brake systems.
Our Iowa DOT CDL air brake “endorsement” practice test offers you a groundbreaking study method to learn the essential operations of these systems. Removing the “L” restriction requires you to pass an official knowledge test and a skills test (including performing an inspection of the air brakes). You must correctly answer at least 80% of the 25 questions on the official knowledge test to receive a passing score. The practice test includes 30 questions that will assess your current proficiency and identify the information you should better understand. You can use the practice test to develop a study plan, track your progress, and determine your readiness for the official knowledge test.
M.S., Chief Educational Researcher (ACES member)
Last verified for accuracy on
This Iowa DOT CDL air brake “endorsement” practice test uses reliable information to help you overcome your learning obstacles. The practice test is based on the most recent Iowa DOT CDL manual (Iowa CDL Handbook 2026) and is up to date as of January 2026. As an authoritative source, the CDL manual provides the information you can depend on to support your answers. If you submit an incorrect answer, the practice test provides a thorough explanation of the correct one with information taken directly from the CDL manual. This approach is a marked departure from the tactics of traditional study methods. Traditional study methods are more one-dimensional and commonly use memorization exercises to teach you. This approach limits you to learning surface knowledge and being minimally prepared to exhibit your skills. In comparison, the practice test interacts with you and guides you in developing a clear understanding of the information you must know. You benefit by having instant access to the information you need to correct your misconceptions, learning how it applies to various driving scenarios, and likely passing the official knowledge test on your first attempt.
Common Chord promotes the power of music to improve communities, and you can develop harmonious driving skills using the practice tests at https://driving-tests.org/iowa/.
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 2026 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.
