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In Iowa, all drivers are required to have a Tank (N) endorsement to operate vehicles designed to transport significant quantities of liquid or gaseous materials in tanks. With a tank (N) endorsement, you are allowed to transport liquids or gases in tanks individually rated at 119 gallons or more, or with a combined capacity of 1,000 gallons or more.
To obtain such an endorsement on their commercial driver’s license (CDL), all drivers must pass a knowledge test that covers the unique operational procedures associated with these vehicles. After all, you’re responsible for transporting a high volume of potentially dangerous liquids or gases, so it is crucial that you get proper training and master specific aspects such as the dynamics of liquid movement.
Aspiring students who are obtaining a CDL for the first time will also need to pass the standard CDL skills test, which includes a pre-trip inspection, a basic control skills test and a road test. You must pass these tests in a vehicle that is representative of the class of CDL you’re applying for.
There are plenty of online resources that help you prepare for the written exam. While you may already be familiar with the official 2025 CDL manual (https://driving-tests.org/iowa/ia-cdl-handbook/), it’s better to also practice and test the knowledge you have just gained. Our CDL Tanker practice tests are a great place to start since they closely reflect the official exam. Each practice test has 20 questions and is current for December 2025.
M.S., Chief Educational Researcher (ACES member)
Last verified for accuracy on
To pass each practice test, you’ll need to provide a correct answer to 80% of the questions. While there are multiple answer options, keep in mind that only one of them is correct. Since there is no time limit, you won’t feel the pressure of a countdown. Take your time to fully understand the question and pick the answer that makes the most sense to you. Detailed feedback is provided after each question, and the question comes with a detailed explanation, so you won’t have to wait until the end to know what went wrong.
Your commercial driver’s license (CDL) is not transferable if you move to another state. Since you’ll have to obtain this endorsement again, make sure to check our tanker endorsement test collection. It features a detailed guide and similar practice tests for all 50 US states, plus Washington, DC.
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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.
