Free Iowa CDL practice test online
Take a free Iowa CDL practice exam online with clear explanations—no sign-up. Coverage includes general knowledge, vehicle systems, combination vehicles, cargo, and endorsements. Then verify current requirements with Iowa Department of Transportation.
Iowa Department of Transportation gives the general knowledge test as 50 questions, and federal law sets the bar at 80% correct on every knowledge test. You must also hold a commercial learner’s permit for 14 days before the skills test.
New to the knowledge test? CDL endorsements explained · One-week study plan
Requirements before you test
Iowa CDL test requirements
Commercial licensing is largely federal. Any figure above credited to a 49 CFR section applies in every state — see 49 CFR 383.135(a)(1) and 49 CFR 383.25(e). A figure credited to Iowa Department of Transportation is Iowa’s own, and may be stricter than the federal floor. Test length, fees, and scheduling are set by Iowa Department of Transportation (official source).
Entry-Level Driver Training comes first
Since February 7, 2022, a new Class A or Class B CDL, a class upgrade, or a first passenger, school bus, or hazardous materials endorsement requires training from a provider on the FMCSA Training Provider Registry (49 CFR 380.600). Practice questions are study material and do not satisfy that requirement.
FMCSA Training Provider RegistryYou need a Iowa licence first
A commercial learner’s permit only counts if you already hold an ordinary licence from the same state (49 CFR 383.25(a)(2)). The Iowa non-commercial knowledge test runs 35 questions and needs 28 correct, with permits issued from age 14.
Iowa permit practice testWhat you will practice
Build coverage topic by topic.
Each question carries a topic, difficulty, explanation, and source section so your review has context.
Sample questions
5 Iowa CDL practice questions
Try these Iowa sample questions now — each shows the correct answer with a plain-language explanation and a source section. The full 600-question bank is in the practice run.
1. When inspecting trailer air lines, you are checking that they are not:
- Crimped, tangled, or dragging on the ground
- BAttached to the glad hands
- CFitted with rubber seals
- DColour coded
Answer: Crimped, tangled, or dragging on the ground. A crimped line restricts air, and a dragging line can be torn away, causing a sudden loss of braking.
Source: Commercial Driver License Manual — Combination vehicles — air lines
2. Battery fluid and hydrochloric acid are examples of Hazard Class:
- A1
- B3
- C7
- 8
Answer: 8. Class 8 covers corrosives such as acids and battery fluid that can burn skin or damage materials on contact.
Source: Commercial Driver License Manual — Hazardous materials — hazard classes
3. When transporting Division 1.1, 1.2, or 1.3 explosives, you must have:
- AA tank endorsement only
- BOnly verbal directions from the shipper
- A written route plan and follow it
- DNo shipping papers if placarded
Answer: A written route plan and follow it. Carriers prepare the plan in advance. Keep a copy with you; deliver only to authorized persons or proper locked storage.
Source: Commercial Driver License Manual — Hazardous materials — explosives routing
4. Smooth-bore (unbaffled) tanks have very strong forward-and-back surge because:
- AThey are always empty
- Nothing inside slows the liquid flow
- CThey use solid bulkheads with no holes
- DABS is required
Answer: Nothing inside slows the liquid flow. Food tanks often omit baffles for sanitation. Start and stop extremely carefully.
Source: Commercial Driver License Manual — Tank vehicles — unbaffled tanks
5. Front tires on a truck or truck tractor need at least how much tread in a major groove?
- 4/32 inch
- B1/32 inch
- C8/32 inch
- D2/32 inch
Answer: 4/32 inch. Other tires generally need at least 2/32 inch. Use a gauge—do not guess in winter conditions.
Source: Commercial Driver License Manual — Vehicle inspection — tires
CDL knowledge areas
Classes and endorsements, organized.
Each area below scopes the reviewed question bank to one knowledge test. The material is federal, so it applies in Iowa just like everywhere else — the endorsement guide explains how the codes fit together.
The foundation for commercial driving: inspections, space, speed, communication, hazards, and safe operation.
- Pre-trip inspection
- Space and speed management
- Railroad crossings
- Emergency procedures
Understand air-brake components, inspections, warning devices, stopping distance, and controlled braking.
- Dual air systems
- Low-air warnings
- Brake lag and fade
- Applied-leak and static checks
Prepare for safe coupling, inspection, turning, backing, and handling of tractor-trailer combinations.
- Fifth-wheel inspection
- Coupling and uncoupling
- Off-tracking
- Trailer skid prevention
Study hazard communication, shipping papers, placards, loading rules, parking, and emergency response responsibilities.
- Hazard classes
- Placards and labels
- Shipping papers
- Loading and segregation
Learn how liquid surge, outage, bulkheads, and high centers of gravity change vehicle handling.
- Liquid surge
- Outage requirements
- Smooth braking
- Rollover prevention
Practice converter-dolly inspection, coupling order, rearward amplification, and stability principles.
- Coupling sequence
- Converter dollies
- Rearward amplification
- Space management
Prepare to inspect, load, and operate buses while keeping passengers, aisles, and exits safe.
- Vehicle inspection
- Passenger loading
- Emergency exits
- Prohibited practices
Review student loading, danger zones, mirrors, emergency procedures, and special railroad-crossing duties.
- Danger zones
- Student loading
- Mirror use
- Railroad crossings
More midwest practice
Nearby CDL practice tests
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Common questions
What this practice can—and cannot—tell you.