Free Idaho DMV CDL — General Knowledge Practice Test 2026
The Idaho CDL — General Knowledge knowledge test has ~50 questions, and you need ~40 correct (80%) to pass. Practice free with questions written from the official Idaho driver handbook — every one has a clear explanation, and you can retake as often as you like with no sign-up.
Content reviewed against official driver handbooks · August 12, 2026
What's on the Idaho written test
The Idaho CDL — General Knowledge knowledge test has ~50 questions; you need ~40 correct (80%) to pass.
Based on the official Idaho exam format — always confirm current details with your state DMV.
Practice by topic
Focus on one area at a time — each topic has its own set of Idaho practice questions.
Learn the shapes, colors, and meanings of regulatory, warning, and guide signs — from stop and yield to construction and school-zone signs.
Speed limits, turning and signaling rules, headlight and seat-belt requirements, and the everyday laws every driver must follow.
How to read traffic signals, lane lines, and pavement markings — including yellow and white lines, arrows, and flashing lights.
Who goes first at intersections, four-way stops, roundabouts, and crosswalks, and how to yield to pedestrians and emergency vehicles.
Following distance, scanning, blind spots, using your lights, and the habits that prevent crashes and keep you in control.
Driving safely around motorcycles, bicycles, large trucks, pedestrians, and school buses — and knowing who has the right of way.
Blood alcohol limits, zero-tolerance and implied-consent laws, and how alcohol and drugs — legal or not — affect your driving.
Legal and illegal parking, colored curbs, distances from hydrants and crossings, and how to park safely on hills.
Choosing a safe speed, keeping a space cushion, adjusting for weather and traffic, and understanding stopping distance.
What to do when things go wrong — brake failure, tire blowouts, skids, and stalling on railroad tracks.
The point system, license suspension, provisional-license rules, insurance requirements, and other licensing basics.
How to pass the first time
- Read the official Idaho driver handbook at least once before test day.
- Practice by topic to find your weak spots, then fix them.
- Take full-length practice tests until you pass comfortably every time.
- Read every explanation — understanding beats memorizing.
Idaho CDL — General Knowledge test — frequently asked questions
How many questions are on the Idaho CDL — General Knowledge test?
The Idaho CDL — General Knowledge knowledge test has ~50 questions, and you need ~40 correct (80%) to pass. Our practice tests mirror that format.
How many questions can I miss on the Idaho CDL — General Knowledge test?
You can miss up to ~10 of the ~50 questions and still pass — you need ~40 correct, which is 80%.
Can I retake the practice test?
Yes — practice as often as you like, completely free. The questions and answer choices are shuffled each time.
Can I take the Idaho practice test in Spanish?
Yes. Every question here is available in English and Spanish — switch languages anytime. Many states also offer the real knowledge test in languages other than English; confirm what Idaho offers with your DMV.
Can I practice on my phone?
Yes. The practice tests work in any mobile or desktop browser — no app or sign-up needed — so you can study anywhere.
Are these the real DMV test questions?
No. Our questions are original, written from the current official Idaho driver handbook to match the real test's topics and style. We are not affiliated with any DMV or government agency.
What's the best way to study?
Read the Idaho driver handbook, practice by topic to target weak areas, and finish with full-length tests until you consistently pass.
Other Idaho practice tests
Take the CDL — General Knowledge test in another state
Every Idaho question is written from the official Idaho driver handbook and checked against its current edition. DMV Test Free is a free, independent study resource — not affiliated with any DMV or government agency. About DMV Test Free
Idaho CDL — General Knowledge questions with answers
20 sample questions from the Idaho CDL — General Knowledge question bank — each with the correct answer, a short explanation, and the section of the official handbook it comes from.
Show all 20 questions with answers
1. When may you run your engine while loading or unloading flammable liquids from a cargo tank?
Correct answer: Only if the engine is needed to operate a pump
The engine is shut off before flammable liquids are loaded or unloaded. The one exception is when the engine has to run a pump.
Source: Idaho Commercial Driver's License Manual — Section 9.5.3, Flammable Liquids
2. In a tank vehicle, what can happen if you steer quickly while braking?
Correct answer: The vehicle may roll over
The manual tells tanker drivers who must stop fast to use controlled or stab braking, and warns that quick steering during braking can put the vehicle on its side.
Source: Idaho Commercial Driver's License Manual — Section 8.3.2, Controlling Surge
3. How are two glad hands brought together when you connect trailer air lines?
Correct answer: Hold the couplers at right angles with their seals touching, then twist the hose-side coupler to lock
After cleaning the couplers and seals, you bring the seals together with the two couplers set at 90 degrees to one another. Turning the glad hand on the hose then joins and locks them.
Source: Idaho Commercial Driver's License Manual — Section 6.2.5, Hose Couplers (Glad Hands)
4. When planning for a school bus evacuation, how does the manual suggest using student assistants where possible?
Correct answer: Two responsible, older students at each emergency exit, plus another to lead the group to a safe place
The plan is to put a pair of older, dependable students at every emergency exit to help others off, and to name one more to lead everyone to the safe place. Because such students may not be aboard, every student still has to be taught the procedures.
Source: Idaho Commercial Driver's License Manual — Section 10.3.2, Evacuation Procedures
5. How far from the business or farm being serviced does Idaho's Seasonal CDL remain valid?
Correct answer: Within 150 miles
The seasonal CDL is good only inside a 150-mile radius of the farm or business the driver is serving.
Source: Idaho Commercial Driver's License Manual — Seasonal CDL for Farm-Related Services
6. How did the Clearinghouse come to be established, according to the manual?
Correct answer: Congress passed a law telling the Secretary of Transportation to set it up
The manual explains that Congress, by statute, had the Secretary of Transportation create the Clearinghouse.
Source: Idaho Commercial Driver's License Manual — Drug & Alcohol Clearinghouse
7. A student who has to cross the road reaches the edge of the roadway in front of your school bus. Besides looking in all directions, what should the student check on the bus before waiting for your signal?
Correct answer: That the red flashing lights are still flashing
At the roadway edge students should stop, look every way, confirm the bus's red lights are still flashing, and then wait for the driver's signal to cross.
Source: Idaho Commercial Driver's License Manual — Section 10.2.3, Unloading Procedures on the Route
8. Once a portable tank is loaded on your truck, its identification numbers can no longer be seen. What must you do?
Correct answer: Put the number on the truck itself, on both of its sides and both of its ends
The numbers have to remain visible with the tank on the vehicle. When they aren't, the identification number must go on the motor vehicle itself, on its two sides and its two ends.
Source: Idaho Commercial Driver's License Manual — Section 9.5.1, Markings
9. A leaking hazmat load contaminates parking lots, roadways and drainage ditches. Who pays for the cleanup, according to the manual?
Correct answer: The carrier
The manual reminds drivers that cleanup costs fall on the carrier and are enormous, which is one reason never to keep driving with material leaking and leave a long trail of contamination.
Source: Idaho Commercial Driver's License Manual — Section 9.7.3, Fires
10. Your bus approaches a drawbridge where a traffic light is showing green. What must you do?
Correct answer: Slow down and make sure it is safe; a full stop is not required
Buses stop at drawbridges that have no signal light or attendant. With a green light, or with an attendant or officer controlling traffic when the bridge opens, the bus only has to slow and confirm it is safe.
Source: Idaho Commercial Driver's License Manual — Section 4.3.6, Drawbridges
11. Which of these is among the requirements to apply for Idaho's Seasonal CDL?
Correct answer: Be at least 16 and hold a valid Class D license
Applicants must be at least 16, hold a valid Class D license and have a year or more of driving experience, along with a clean record on the listed offenses.
Source: Idaho Commercial Driver's License Manual — Seasonal CDL for Farm-Related Services
12. When may a placarded vehicle with no explosives aboard be parked less than five feet from the traveled portion of the road?
Correct answer: Only if your work requires it, and then only briefly
Parking that close is permitted only when the job makes it necessary, and it should be kept short. Someone must watch the vehicle whenever it sits on a public road or its shoulder.
Source: Idaho Commercial Driver's License Manual — Section 9.6.2, Parking a Placarded Vehicle Not Transporting Division 1.1, 1.2, or 1.3 Explosives
13. Why might a tank be filled only partway with a dense liquid such as some acids?
Correct answer: A full tank of it could exceed legal weight limits
Heavy liquids can put a vehicle over the legal weight before the tank is full, so tanks of dense liquid are often only partly filled. How much to load depends on expansion in transit, the liquid's weight and the legal limits.
Source: Idaho Commercial Driver's License Manual — Section 8.2.7, How Much to Load?
14. Compared with empty rigs, how much more likely are fully loaded rigs to roll over in a crash?
Correct answer: Ten times as likely
The combination vehicles section puts the rollover risk of a fully loaded rig in a crash at ten times that of an empty one, because piled-up cargo raises the center of gravity.
Source: Idaho Commercial Driver's License Manual — Section 6.1.1, Rollover Risks
15. A rider wants to bring a car battery and a can of gasoline onto your bus. What does the manual say?
Correct answer: Don't let riders bring common hazards like these aboard
Riders sometimes board with unlabeled hazardous materials. The manual names car batteries and gasoline as common hazards that riders should not be allowed to carry on.
Source: Idaho Commercial Driver's License Manual — Section 4.2.2, Forbidden Hazardous Materials
16. A truck-and-trailer combination rated over 10,000 pounds GVWR is used in commerce across state lines, but its driver does not need a CDL. What does Idaho's manual say?
Correct answer: It still falls under Federal Motor Carrier requirements, and the manual refers the operator to the Idaho State Police's Commercial Vehicle Safety office
Vehicles above 10,000 pounds GVWR that work in commerce across state lines come under Federal Motor Carrier requirements even when no CDL is needed. The manual sends their operators to Idaho State Police, Commercial Vehicle Safety, for guidance.
Source: Idaho Commercial Driver's License Manual — Commercial Vehicle Exemptions
17. Which alcohol-related history disqualifies an applicant for Idaho's Seasonal CDL?
Correct answer: Any DUI conviction, for alcohol or a controlled substance and in any vehicle, with a test refusal counting too
Seasonal CDL applicants must have no conviction, in any vehicle, for impaired driving involving alcohol or a controlled substance, and the manual counts a refusal to test as well.
Source: Idaho Commercial Driver's License Manual — Seasonal CDL for Farm-Related Services
18. Your intercity bus has a restroom. Which signaling device does the manual say must be in safe working condition before you drive?
Correct answer: The restroom emergency buzzer
Signaling devices are on the list of bus interior items that must work, and the list specifically includes the restroom emergency buzzer on buses that have a restroom.
Source: Idaho Commercial Driver's License Manual — Section 4.1.3, Bus Interior
19. A radioactive package is labeled Radioactive II or Radioactive III. What number does the shipper print on that label?
Correct answer: The package's transport index
Some Class 7 packages carry a transport index, which the shipper prints on the Radioactive II or III label. It tells how much control the package needs in transit, and the indexes in one vehicle may not add up to more than 50.
Source: Idaho Commercial Driver's License Manual — Section 9.4.1, General Loading Requirements
20. What was CHEMTREC, the Chemical Transportation Emergency Center, created to provide?
Correct answer: Technical details on how hazardous materials behave physically, for use by emergency personnel
CHEMTREC runs a 24-hour toll-free line that gives emergency personnel technical information on hazardous materials' physical properties. It and the National Response Center keep in close touch and pass problems to each other.
Source: Idaho Commercial Driver's License Manual — Section 9.7.5, Required Notification