Idaho General Knowledge CDL Practice Test
25 realistic General Knowledge practice questions for Idaho CDL applicants. Required for: All CDL applicants (Class A, B, and C). Official test: 50 questions, 40 correct to pass.
Question 1 of 25 · Adverse Conditions
What should you do before driving in fog?
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A.
Use high beams to see further
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B.
Slow down and use low beams and fog lights if equipped
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C.
Speed up to clear the fog area
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D.
Follow another vehicle closely
Correct answer: B.
Slow down before entering fog. Use low beams and any installed fog lights.
Question 2 of 25 · Adverse Conditions
When you have to drive into the sun and visibility is reduced, what should you do?
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A.
Use sunglasses and lower the visor
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B.
Use only your high beams
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C.
Maintain your normal speed
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D.
Speed up to get past the area
Correct answer: A.
Use sunglasses and the visor and slow down. Reduced visibility increases stopping distance.
Question 3 of 25 · Communication
When should you check your mirrors?
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A.
Only before changing lanes
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B.
Frequently, to know what is around your vehicle
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C.
When parking only
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D.
Only at intersections
Correct answer: B.
Check mirrors regularly to know what is happening around your vehicle.
Question 4 of 25 · Basic Control
Which of these is the proper way to hold a steering wheel?
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A.
One hand at 12 o'clock
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B.
Both hands on opposite sides of the wheel
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C.
Both hands on top
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D.
One hand at 6 o'clock
Correct answer: B.
Hold the wheel firmly with both hands placed on opposite sides for full control.
Question 5 of 25 · Night Driving
You should use low beam headlights:
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A.
Whenever you can
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B.
Within 500 feet of an oncoming vehicle and 500 feet behind another vehicle
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C.
Only in fog
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D.
On lighted city streets only
Correct answer: B.
Use low beams within 500 feet of oncoming traffic and when following within 500 feet of another vehicle.
Question 6 of 25 · Basic Control
Convex (curved) mirrors:
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A.
Make objects appear larger and closer than they really are
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B.
Make objects appear smaller and farther away than they really are
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C.
Provide a normal view
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D.
Are required only on doubles
Correct answer: B.
Convex mirrors widen the field of view but make objects look smaller and farther away.
Question 7 of 25 · Speed Management
When approaching a curve, you should:
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A.
Brake while in the curve
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B.
Slow down before entering the curve
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C.
Maintain highway speed
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D.
Use the engine brake throughout
Correct answer: B.
Reduce speed before entering the curve, then accelerate slightly through the curve for stability.
Question 8 of 25 · CDL Rules
Driving with a BAC of 0.04 or higher in a CMV will result in:
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A.
A warning
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B.
A 30-day suspension
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C.
A CDL disqualification of at least one year
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D.
No penalty if off-duty
Correct answer: C.
A first offense disqualifies you for at least one year (three years if hauling hazardous materials).
Question 9 of 25 · Inspection
Pre-trip inspection of the vehicle should be done in the same order each time so that you:
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A.
Will look professional to other drivers
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B.
Will learn it well and not skip anything
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C.
Can finish faster
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D.
Pass the test more easily
Correct answer: B.
Following the same order helps prevent missed steps and builds reliable habits.
Question 10 of 25 · CDL Rules
Refusing a chemical test for alcohol or drugs while operating a CMV will result in:
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A.
A warning
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B.
A 90-day suspension
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C.
CDL disqualification of at least one year
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D.
A simple fine
Correct answer: C.
Refusal is treated the same as testing positive — minimum one-year disqualification.
Question 11 of 25 · Emergency Maneuvers
Controlled braking is:
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A.
Pressing the brake to the floor and holding
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B.
Applying brakes hard enough to lock the wheels
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C.
Applying brakes to keep wheels just short of locking
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D.
Releasing brakes and coasting
Correct answer: C.
Controlled braking applies the brake firmly without locking the wheels, keeping the steering straight.
Question 12 of 25 · Cargo
Which is true about cargo securement?
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A.
Drivers are responsible for inspecting cargo
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B.
Cargo only needs to be inspected at the start of a trip
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C.
Securement is the shipper's sole responsibility
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D.
Once strapped, cargo never needs re-checking
Correct answer: A.
Drivers must inspect cargo and its securement at the start of the trip and re-check periodically.
Question 13 of 25 · Driver Wellness
You should not eat or drink while driving because:
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A.
It is illegal in all states
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B.
Spills can distract you
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C.
You should not put both hands on the wheel
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D.
It might damage the vehicle
Correct answer: B.
Eating and drinking divert attention and create spill hazards.
Question 14 of 25 · Speed Management
Engine brakes (Jakes) should not be used:
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A.
On dry pavement at highway speed
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B.
On slippery roads while loaded or empty
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C.
When descending a steep grade
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D.
Heading toward a long downhill
Correct answer: B.
Avoid engine brakes on slippery roads — they can cause the drive wheels to lose traction.
Question 15 of 25 · Hazard Awareness
Hazardous conditions exist when there are:
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A.
Pedestrians and bicyclists
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B.
Children and elderly drivers
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C.
Distractions and bad weather
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D.
All of the above
Correct answer: D.
Hazards include other road users, weather, distractions, and changing road surfaces.
Question 16 of 25 · Mountain Driving
What may happen if you don't shift gears properly when going up a hill?
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A.
You will use less fuel
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B.
The transmission will be damaged
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C.
You may lose control on a downgrade
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D.
Engine RPM will be too low
Correct answer: C.
Improper gear use can result in losing control of speed, especially on the way back down a hill.
Question 17 of 25 · Driver Wellness
Which of these statements about staying alert to drive is true?
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A.
Coffee will overcome fatigue
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B.
You can rely on caffeine to stay awake
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C.
There is no substitute for sleep
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D.
Cold air will keep you alert all night
Correct answer: C.
There is no substitute for adequate rest. Caffeine and cold air provide only temporary alertness.
Question 18 of 25 · Inspection
Vehicle inspection is important because:
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A.
Federal and state laws require it
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B.
Safety is at risk
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C.
Defects can save lives if found early
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D.
All of the above
Correct answer: D.
Inspections are legally required and prevent breakdowns and crashes by catching defects early.
Question 19 of 25 · Adverse Conditions
Black ice is:
-
A.
A thick layer of ice that is easily seen
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B.
A thin layer that looks wet pavement
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C.
Only found in the far north
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D.
Not a real road hazard
Correct answer: B.
Black ice is a thin, transparent layer that looks like wet pavement. It is extremely dangerous.
Question 20 of 25 · Adverse Conditions
Which of the following is true about driving in fog?
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A.
You should always drive with high beams
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B.
Avoid driving in fog if possible
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C.
Use the right edge of the road as a guide rather than the center line
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D.
Both b and c
Correct answer: D.
Avoid driving in fog when possible. If unavoidable, use low beams and the right edge as a guide.
Question 21 of 25 · Speed Management
The total stopping distance of a CDL vehicle includes:
-
A.
Perception, reaction, and braking distance
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B.
Only braking distance
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C.
Following distance and brake lag
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D.
Only the distance traveled while braking
Correct answer: A.
Total stopping distance is the sum of perception distance, reaction distance, brake lag, and braking distance.
Question 22 of 25 · CDL Rules
What is the legal blood alcohol concentration (BAC) limit for CDL drivers?
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A.
0.08%
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B.
0.05%
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C.
0.04%
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D.
0.02%
Correct answer: C.
Federal CDL law sets the BAC limit at 0.04%, half the limit for non-commercial drivers.
Question 23 of 25 · Hours of Service
How often must a driver complete a written record of duty status?
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A.
Every 8 hours
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B.
Every 12 hours
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C.
Every 24 hours
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D.
Once a week
Correct answer: C.
A daily record of duty status (logbook) must be completed each 24-hour period.
Question 24 of 25 · Speed Management
You are driving a vehicle that could safely be driven at 55 mph on an open highway. The traffic is heavy and moving at 35 mph. The safest speed for your vehicle in this traffic is most likely:
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A.
25 mph
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B.
35 mph
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C.
45 mph
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D.
55 mph
Correct answer: B.
You should generally adjust to the speed of surrounding traffic when it is safe to do so.
Question 25 of 25 · Cargo
Which is correct about cargo and weight balance?
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A.
Heavy cargo should always be at the rear
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B.
Cargo should be balanced and secured to prevent shifting
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C.
Side-to-side balance does not matter
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D.
Top-heavy loads improve stability
Correct answer: B.
Cargo must be evenly balanced and well secured. Top-heavy loads increase rollover risk.
About the General Knowledge Test
The General Knowledge test covers safe vehicle inspection, basic vehicle control, shifting gears, communicating, controlling speed, controlling distance, seeing hazards, distracted driving, aggressive drivers, communicating with other drivers, night driving, driving in fog, winter driving, hot weather driving, mountain driving, driving emergencies, anti-lock braking systems, skid recovery, accident procedures, fires, alcohol and other drugs, hazardous materials awareness, and staying alert and fit to drive. Every commercial driver in the United States must pass this test before any other CDL endorsement can be added.
The Idaho Transportation Department — Driver Services administers this knowledge test as part of its commercial driver license program. To earn the CDL General Knowledge on your Idaho CDL, you need to score at least 40 out of 50 on the official version.
Topics covered on this practice test
- Adverse Conditions: 4 questions
- Speed Management: 4 questions
- CDL Rules: 3 questions
- Basic Control: 2 questions
- Inspection: 2 questions
- Cargo: 2 questions
- Driver Wellness: 2 questions
- Communication: 1 question
- Night Driving: 1 question
- Emergency Maneuvers: 1 question
- Hazard Awareness: 1 question
- Mountain Driving: 1 question
- Hours of Service: 1 question
How to use this practice test
- Read each question carefully. CDL questions are written precisely — small wording differences matter.
- Click "Show Answers & Explanations" only after answering every question. Don't peek mid-test.
- Read the explanation for every question, even ones you got right. The reasoning is more important than the answer.
- Repeat the test until you score 100%. The questions are deterministic per state, so you can track your improvement over multiple sessions.
- Move on to the other endorsement tests for Idaho until you're ready for the official exam.
Tips specific to the General Knowledge test
The General Knowledge test is the foundation of every CDL. Topics include vehicle inspection, basic control, shifting, communicating, controlling speed, controlling space, hazard perception, distracted driving, night driving, fog, winter, hot weather, mountain driving, emergencies, anti-lock brakes, skid recovery, accident procedures, fires, alcohol, hazardous materials awareness, and staying alert. Most failures come from speeding through inspection-related questions; slow down and read carefully.
Other practice tests for Idaho