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Practice for your General Knowledge CDL exam with questions based on the official Idaho CDL handbook
What should you do when merging?
When you're getting onto a road, make sure there's enough room for your vehicle by checking your mirrors. You should merge into traffic smoothly without going a lot slower than other cars and always signal to let others know what you're doing.
Documents related to hazardous materials transportation must be stored ___.
Keep the papers for hazardous materials in the driver door pouch. This way, they are easy to reach if needed.
Which of these statements about driving through a tunnel is correct?
When you drive out of a tunnel, you might feel a strong push of wind.
Among these vehicles, which is more likely to experience off-tracking during turns?
When a big truck turns, the back end can swing out. This is called off-tracking. A tractor with a 45-feet trailer is more likely to do this because it's longer and the way it's put together makes the back end swing out more when it turns.
Under what circumstances should you sound your horn?
Use your horn only if it can help stop an accident from happening.
Identify the incorrect statement regarding alcohol consumption.
A drinker can't control how fast his or her body absorbs alcohol.
If your vehicle is missing ____ or more leaves from any leaf spring, it won't be allowed to be used.
If a quarter or more of the leaves in any leaf spring are missing, your truck can't be used until it's fixed.
Select the correct statement regarding the transportation of hazardous materials.
Hazardous materials are always dangerous to health and safety, no matter what kind they are. They can hurt people and the environment, so it's important to handle them carefully.
To figure out how much alcohol is in someone's blood (BAC), you need to know:
An individual's body weight plays a central role in determining how alcohol disperses throughout the body. Essentially, a lighter person will have a higher concentration of alcohol in their bloodstream after consuming the same amount as someone heavier.
What is the right way to hold a steering wheel?
The correct way to hold a steering wheel is with both hands placed on opposite sides of the wheel. This gives you the most control over the vehicle, making it safer to drive.
What statement about the use of drugs is correct?
Using drugs can make driving unsafe and might get you into an accident or even get you arrested.
Specify the conditions under which a driver without a hazardous materials endorsement is allowed to drive a vehicle carrying hazardous substances.
If the hazardous materials being transported do not require placarding under federal and state regulations, a driver without a HazMat endorsement may operate the vehicle.
What would be your total stopping distance at 55 mph on dry pavement?
If you're driving at 55 mph on a dry road and need to stop, you'll need as much space as a football field to do so safely.
What should you do if you see a hazard on the road ahead?
When you see something dangerous on the road ahead, the best thing to do is turn on your emergency lights or tap your brakes to alert other drivers. Never get too close to the car in front as a shield, and don't just turn on your bright lights. This way, everyone can stay safe.
What is the safest method to merge onto the road?
Merging onto a road safely means finding a big enough space in traffic so you can join in without causing problems. This way, cars have room to adjust and you can blend in smoothly.
What statement about loading cargo is correct?
The weight limit is determined by the state in which you are operating.
What is the appropriate action if the drive wheels begin to spin when you start moving from a stationary position?
If your wheels are tugging when you start driving, simply take your foot off the accelerator pedal.
What should you do when a heavy load slows you down while ascending an incline?
If your truck is carrying a heavy load and it's making you slow down while going uphill, you should switch to a lower gear. This helps your truck gain more power to move up the hill easier.
How should you arrange reflective triangles when parking on the roadside of a straight, level, four-lane divided highway?
When parking on a straight, level, four-lane divided highway, place one within 10 feet of the rear of the vehicle, one about 100 feet to the rear, and one about 200 feet behind your vehicle for safety.
Which of the following statements regarding the pre-trip inspection of your wheels and rims is true?
Rust around the wheel nuts can be a sign that they are not tight enough. Always check this before a trip.
Identify the correct practice regarding engine overheating.
If your engine is too hot, don't take off the radiator cap if the engine hasn't cooled down. Driving when the temp gauge is in the red or with not enough coolant can make things worse.
Select the statement that is false regarding the procedure for reversing a heavy vehicle.
When maneuvering a heavy vehicle, every movement must be precise and controlled. Relying on a slight bump as a guide introduces risks of misjudging distance, causing damage to both the vehicle and the dock.
When driving a large vehicle that moves slower than other traffic, which guideline should you AVOID following?
You should avoid signaling other drivers when it is safe to pass because it is their responsibility to judge the road conditions and determine when passing is safe. Instead of signaling, focus on maintaining a steady speed, staying in the right lane when possible, and allowing other drivers to make their own safe decisions about passing.
What is true regarding taking emergency or evasive maneuvers?
When you need to turn quickly in an emergency, make sure you're holding the steering wheel tightly to control the vehicle properly.
When driving at the usual speed on a highway, you should try to look ahead of your car for about ___ miles.
When you are traveling at usual speed on a highway, try to look ahead about 1/4 mile. This way you can see what is happening ahead and stay safe.
Which brake system should be checked when the vehicle is stationary?
When your vehicle is not moving, check if the steering wheel is firm and doesn't move too much. Also, test the hydraulic brakes to ensure they are working properly.
Identify the accurate statement regarding the operation and effect of brakes.
When a vehicle is heavier or moving fast, its brakes need to soak up more heat to make it stop.
What is accurate about the impact of hot weather on tires during driving?
When it's really hot, check your tires every 2 hours or 100 miles to make sure they're okay. Driving slow or using winter tires won't help in the heat.
After turning on the engine:
After you start your truck's engine, watch the coolant temperature gauge. It should slowly start to go up until it reaches the normal range. This shows your engine is warming up properly.
Which action should you AVOID when aiding injured individuals at the site of an accident?
It is important to keep injured individuals warm to prevent shock. Cooling them down could worsen their condition, especially if they are in shock or suffering from blood loss.
Identify the correct statement from the following.
Most big vehicle crashes happen between midnight and 6 a.m. This is because it's harder to see, and drivers might be tired. So, driving big vehicles at night can be more dangerous, not just because of less traffic or using less fuel.
How far ahead should a driver be looking while operating the vehicle?
When driving, it's best to look 12-15 seconds ahead on the road. This means if you're going faster, you'll look further ahead. For example, in the city, this could be about one block ahead. Looking far ahead helps you see problems early, so you have more time to react and keep safe.
What is a safety measure to follow when setting up reflective triangles?
When setting up safety triangles, keep them between you and the cars coming your way. This helps cars see you and the triangles better, keeping you safe.
What statement regarding the behavior of other drivers on the road is true?
Many people driving rented trucks for just a day or a short time aren't used to the poor visibility these big vehicles have. This can make them risky on the road.
What statement is accurate concerning drug consumption and driving?
If a doctor says your prescription medicine won't mess with your driving, it's okay to use it. But, just because you can buy medicine without a prescription doesn't mean it's safe to drive after taking it. Taking medicine is okay if it doesn't affect your driving, no matter the time.
Under which circumstance is it advisable to gently tap your brakes to activate the brake lights?
When you're about to leave the road and need to slow down, gently press your brakes to make your brake lights blink. This will alert drivers behind you that you're slowing down.
How should you respond if your vehicle begins to hydroplane?
When your vehicle slides on water, ease off the gas pedal slowly. Don't turn the steering wheel fast or turn on your lights. This will help you regain control.
Identify the accurate statement concerning overhead clearance.
The weight of your vehicle can make it taller or shorter, changing how much room you need to clear things above. Always add a bit more space above your vehicle to be safe.
At what blood alcohol concentration (BAC) level will you be subject to a 24-hour out-of-service order?
If you have any alcohol in your body that can be measured, you won't be allowed to drive for a day.
What is accurate regarding a skid caused by the rear drive wheels locking?
When the back wheels of a vehicle with a trailer skid, the trailer can push the vehicle to the side, making it slide sideways.
Identify the true statement related to accelerating a vehicle.
Roughly speeding up your vehicle can break parts of it.
Backing of the commercial vehicle is _____ .
Backing up a big truck is always dangerous. You should avoid doing it as much as you can. If you must back up, make sure to check everything carefully and go slow.
Why is it dangerous if the exhaust system is damaged?
If your truck's exhaust system is damaged, harmful gases can get inside where you sit or sleep, which is very dangerous for your health.
What is accurate regarding the procedure for notifying authorities after an accident?
If you're in an accident, use your phone or CB radio right away to tell the cops before you get out of your vehicle. Don't wait till later or think it's only needed for highway crashes. Quick action is important.
You must come to a complete stop at a railroad crossing when:
You must stop at a railroad crossing if your truck is carrying something that rules say you must stop for, or if the crossing is on a narrow road where you can't see well.
How should you handle slippery road conditions?
When roads are slippery, it's safest to turn very slowly and gently. This helps prevent the truck from sliding or losing control. Quick turns can be dangerous because the truck might not grip the road well.
What are the possible outcomes of applying wet brakes after driving through heavy rain?
If your truck's brakes get wet from a lot of rain, they might not work right. When you try to stop, the truck could slide out of control, like when the back part swings out. It's like trying to skate on ice; very slippery and hard to steer.
What potential issues could arise from having too little weight on the drive axle of a vehicle?
If a vehicle doesn't have enough weight on the drive axle, it won't grip the road well, leading to poor traction. This means the tires might slip more, especially in bad weather, making it harder to control the vehicle.
Which of the following statements about the pre-trip inspection of your brakes and suspension system is true?
When you check your truck before a trip, make sure the brake parts aren't oily or greasy. This keeps your brakes working right.
You are driving a heavy vehicle and approaching an off-ramp that curves downhill. What is the safest way to exit the highway?
When exiting a highway with a heavy vehicle using a downhill off-ramp that curves, slow down to a safe speed before you start the curve. This helps you control the vehicle better and stay safe.
The General Knowledge test is required for all CDL applicants in Idaho. It covers traffic laws, safe driving techniques, vehicle inspection procedures, cargo handling, and federal regulations every commercial driver must know.
The General Knowledge test is part of the CDL written exam administered by the Idaho Department of Motor Vehicles. You must pass this test along with the other required written tests to receive your Commercial Learner's Permit (CLP) in Idaho.
Our practice questions are built from the official Idaho CDL handbook and federal FMCSA regulations. Each question includes a detailed explanation to help you understand the material, not just memorize answers.
