Use this set after reading the CDL general knowledge outline or when you want a broad check of safe-driving, inspection, cargo, and road-decision topics.
Study the weak area
What to understand before you answer.
This is a mixed CDL practice set. It is useful for finding weak areas before moving into focused drills.
01
Read each question as a real commercial driving decision.
02
Watch for weather, visibility, speed, space, inspection, and cargo clues.
03
Use the explanations after review to decide which focused topic to practice next.
Before the questions
How to improve this score.
Answer every question.
Review the score report and missed explanations.
Open the recommended weak-area drill if one appears.
Retake a mixed set after focused practice.
Common traps to watch for
Backing without a helper or failing to stop when visibility is uncertain.
When this pattern appears in a missed answer, review the explanation before trying another set.
Driving at passenger-car speeds without accounting for weight, space, weather, or grade.
When this pattern appears in a missed answer, review the explanation before trying another set.
Assuming cargo safety is only the shipper or dispatcher responsibility.
When this pattern appears in a missed answer, review the explanation before trying another set.
Memorizing a walk-around order without understanding which defects make the vehicle unsafe.
When this pattern appears in a missed answer, review the explanation before trying another set.
Memorizing rules without applying them to driving scenarios.
When this pattern appears in a missed answer, review the explanation before trying another set.
Practice questions
CDL General Knowledge Test 1 Quiz
Answered 0 / 120
Question 1
When backing a commercial vehicle, which of the following is the most important safety rule?
Because of blind spots, you cannot see everything behind you. Using a helper is the most important safety rule for backing. Always agree on a hand signal for 'stop' before you begin.
Study focusUse safe backing, turning, and basic-control habits.
Common trapBacking without a helper or failing to stop when visibility is uncertain.
Question 2
How far ahead should you be looking while driving a commercial vehicle at highway speeds?
Good drivers look 12 to 15 seconds ahead. At highway speeds, this is about a quarter of a mile. This gives you time to adjust speed or change lanes to avoid hazards.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 3
You are driving a heavily loaded vehicle on a steep downgrade. What is the most important factor in determining your safe speed?
Your safe speed on a downgrade depends primarily on the total weight of the vehicle and cargo, the length and steepness of the grade, road conditions, and weather. Heavier vehicles require more braking power to counteract gravity.
Study focusUnderstand cargo weight, securement, and load safety responsibilities.
Common trapAssuming cargo safety is only the shipper or dispatcher responsibility.
Question 4
What is the minimum tread depth required for the front steering tires of a commercial vehicle?
Federal regulations require a minimum tread depth of 4/32 inch in every major groove on front (steering) tires. Other tires require at least 2/32 inch.
Study focusUse pre-trip inspection habits to identify unsafe vehicle-system defects before driving.
Common trapMemorizing a walk-around order without understanding which defects make the vehicle unsafe.
Question 5
When is it appropriate to use your high beams?
Use high beams whenever you can to see further ahead, provided it is safe and legal. You must dim them when within 500 feet of an oncoming vehicle or when following another vehicle within 500 feet.
Study focusApply core CDL safe-driving rules to common road and vehicle situations.
Common trapMemorizing rules without applying them to driving scenarios.
Question 6
Which of the following statements about drinking alcohol and driving is true?
Alcohol first affects judgment and self-control. For commercial drivers, it is illegal to operate a CMV with a BAC of 0.04% or higher, not 0.08%.
Study focusUnderstand state-specific CDL requirements, handbook notes, and licensing context.
Common trapUsing generic CDL knowledge without checking state-specific requirements.
Question 7
What is 'hydroplaning'?
Hydroplaning occurs when water builds up in front of your tires, causing them to lift off the road surface. You lose steering and braking control. To recover, release the accelerator and do not brake hard.
Study focusUse pre-trip inspection habits to identify unsafe vehicle-system defects before driving.
Common trapMemorizing a walk-around order without understanding which defects make the vehicle unsafe.
Question 8
If you experience a tire blowout while driving at highway speeds, what is the FIRST thing you should do?
When a tire blows out, grip the steering wheel firmly and stay off the brakes. Braking hard can cause a skid or loss of control. Let the vehicle slow down naturally before applying brakes gently.
Study focusUse pre-trip inspection habits to identify unsafe vehicle-system defects before driving.
Common trapMemorizing a walk-around order without understanding which defects make the vehicle unsafe.
Question 9
How often should you check your cargo while on the road?
You must inspect the cargo and its securing devices within the first 50 miles after beginning a trip. After that, inspect again after you have driven for 3 hours or 150 miles, whichever comes first.
Study focusUnderstand cargo weight, securement, and load safety responsibilities.
Common trapAssuming cargo safety is only the shipper or dispatcher responsibility.
Question 10
What is the purpose of a pre-trip inspection?
Safety is the most important reason for a pre-trip inspection. Finding and fixing a defect before driving helps prevent breakdowns and crashes on the road.
Study focusUse pre-trip inspection habits to identify unsafe vehicle-system defects before driving.
Common trapMemorizing a walk-around order without understanding which defects make the vehicle unsafe.
Question 11
Which type of fire extinguisher should be used on an electrical fire?
Electrical fires require a B:C or A:B:C rated extinguisher. Using water or water-based foam on an electrical fire can result in a severe electric shock.
Study focusApply safe loading, separation, parking, routing, and emergency-response decisions for hazmat.
Common trapChoosing a convenient action instead of the action that protects people and isolates the hazard.
Question 12
Why should you avoid using the engine brake (Jake brake) on wet or icy roads?
Engine retarders (Jake brakes) apply strong braking force to the drive wheels only. On slippery surfaces, this sudden braking force can cause the drive wheels to lose traction, leading to a dangerous skid.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
Question 13
What is the recommended following distance for a heavy vehicle traveling at 55 mph in ideal conditions?
The rule of thumb is 1 second of following distance for every 10 feet of vehicle length at speeds under 40 mph. For speeds over 40 mph, add 1 additional second. A 60-foot truck at 55 mph needs 7 seconds of space.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 14
What does a broken exhaust system pose the greatest risk of?
A broken exhaust system can allow deadly, odorless carbon monoxide gas to enter the cab, which can cause drowsiness, illness, or death to the driver.
Study focusRecognize placard, label, marking, and hazard-class requirements for hazmat loads.
Common trapFocusing only on the load name and ignoring placards, labels, and hazard class clues.
Question 15
If your vehicle catches fire while driving, what should you do first?
The first step in a vehicle fire is to get the vehicle off the road and stop in an open area, clear of buildings, trees, brush, and other vehicles to prevent the fire from spreading.
Study focusApply safe loading, separation, parking, routing, and emergency-response decisions for hazmat.
Common trapChoosing a convenient action instead of the action that protects people and isolates the hazard.
Question 16
Which of these is a sign of distracted driving?
Eating, using a phone, or reading while driving are major physical and cognitive distractions that take your eyes, hands, and mind away from the critical task of driving.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
Question 17
What should you do if you are being tailgated?
If you are being tailgated, increase the space in front of your vehicle. This allows you to brake more smoothly and gradually, reducing the chance that the tailgater will crash into your rear.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 18
When approaching a curve, what is the best way to handle your speed?
You should brake to a safe speed before entering a curve. Once in the curve, maintain speed or accelerate slightly, as this helps stabilize the vehicle. Never brake hard in a curve.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 19
What is the most common cause of serious vehicle skids?
Most serious skids result from driving too fast for road conditions, over-braking, over-steering, or over-accelerating. Speed is the primary factor in losing traction.
Study focusUse pre-trip inspection habits to identify unsafe vehicle-system defects before driving.
Common trapMemorizing a walk-around order without understanding which defects make the vehicle unsafe.
Question 20
What must you do when placing warning devices (triangles) on a two-lane road with traffic in both directions?
On a two-lane road carrying traffic in both directions, place warning devices within 10 feet of the front or rear corners, about 100 feet behind, and about 100 feet ahead of the vehicle.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
Question 21
When driving a commercial vehicle, how should you adjust your speed for driving at night?
At night, your visibility is limited to the reach of your headlights. You must adjust your speed so you can safely stop within that visible distance.
Study focusUse inspection habits to catch unsafe defects before driving.
Common trapChecking only obvious items and missing brake, tire, coupling, or defect-report steps.
Question 22
What is the most important reason for inspecting your vehicle?
While avoiding fines is good, safety is the primary reason for inspections. A defect found during an inspection can prevent a breakdown or fatal crash.
Study focusUse inspection habits to catch unsafe defects before driving.
Common trapChecking only obvious items and missing brake, tire, coupling, or defect-report steps.
Question 23
If you must pull over to the shoulder on a highway, how quickly must you place your warning devices?
Federal regulations require that emergency warning devices (like reflective triangles) be placed within 10 minutes of stopping on the shoulder or traveled portion of the road.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
Question 24
What should you do if your vehicle begins to hydroplane?
To recover from hydroplaning, release the accelerator and push in the clutch. Do not use the brakes, as this can cause the wheels to lock and result in a skid.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
Question 25
Which of these statements about managing space is true?
Following too closely (tailgating) severely reduces your reaction time and stopping distance, making it a leading cause of crashes.
Study focusUnderstand state-specific CDL requirements, handbook notes, and licensing context.
Common trapUsing generic CDL knowledge without checking state-specific requirements.
Question 26
What is black ice?
Black ice is a thin layer of clear ice. Because it is clear, you can see the dark asphalt underneath, making the road appear wet rather than icy.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
Question 27
When should you check your mirrors while driving?
You should check your mirrors regularly (about every 5 to 8 seconds) to be aware of traffic around you and to monitor your vehicle and trailer.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 28
What is the primary cause of fatal crashes involving commercial vehicles?
Speeding or driving too fast for conditions is the leading cause of fatal crashes involving large trucks.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 29
If you are driving a 60-foot truck at 50 mph, what is the minimum following distance you should maintain?
The rule is 1 second per 10 feet of length, plus 1 second if going over 40 mph. For a 60-foot truck, that is 6 seconds + 1 second = 7 seconds.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 30
What should you do if an aggressive driver is harassing you?
To deal with an aggressive driver, do not engage. Get out of their way, avoid eye contact, ignore gestures, and report them if they are a severe danger.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 31
Which of these fires can you safely use water to extinguish?
Water can be used to cool down a tire fire. Using water on electrical, gasoline, or grease fires can spread the fire or cause electrocution.
Study focusApply safe loading, separation, parking, routing, and emergency-response decisions for hazmat.
Common trapChoosing a convenient action instead of the action that protects people and isolates the hazard.
Question 32
What happens if the drive wheels lose traction and spin?
If the drive wheels lose traction due to over-acceleration or slippery roads, the tractor can spin out, potentially causing a jackknife.
Study focusControl off-tracking, rollover, rearward amplification, and trailer movement risks.
Common trapTurning or steering too sharply without accounting for trailer movement.
Question 33
How does cargo weight affect the height of your vehicle's center of gravity?
Loading heavy cargo high in the trailer raises the center of gravity, making the vehicle top-heavy and much more likely to roll over in a curve or evasive maneuver.
Study focusApply safe loading, separation, parking, routing, and emergency-response decisions for hazmat.
Common trapChoosing a convenient action instead of the action that protects people and isolates the hazard.
Question 34
What is the best way to use the brake pedal on a steep downgrade?
The 'snubbing' technique involves braking firmly to 5 mph below your safe speed, then releasing them to allow cooling, repeating as necessary while the engine brake does most of the work.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 35
Why do empty trucks have longer stopping distances than loaded trucks?
Empty trucks lack the weight to press the tires firmly against the road. When heavy-duty brakes are applied, the tires easily lock up, reducing traction and increasing stopping distance.
Study focusUnderstand cargo weight, securement, and load safety responsibilities.
Common trapAssuming cargo safety is only the shipper or dispatcher responsibility.
Question 36
When backing, why should you back toward the driver's side whenever possible?
Backing toward the driver's side (sight-side backing) allows you to see the path of the trailer directly out your window, rather than relying solely on mirrors for the blind side.
Study focusUse safe backing, turning, and basic-control habits.
Common trapBacking without a helper or failing to stop when visibility is uncertain.
Question 37
What does it mean if a vehicle has a 'slow-moving vehicle' symbol?
A red triangle with an orange center on the rear of a vehicle indicates it is a slow-moving vehicle, such as a tractor or construction equipment, moving at 25 mph or less.
Study focusApply safe loading, separation, parking, routing, and emergency-response decisions for hazmat.
Common trapChoosing a convenient action instead of the action that protects people and isolates the hazard.
Question 38
What should you do before driving in the mountains?
Mountain driving puts extreme stress on brakes. You must ensure your brakes are in perfect condition and know the route, including the location of runaway truck ramps.
Study focusApply safe loading, separation, parking, routing, and emergency-response decisions for hazmat.
Common trapChoosing a convenient action instead of the action that protects people and isolates the hazard.
Question 39
Which of these is NOT a good rule to follow when caring for an injured person at a crash scene?
You should NEVER move a severely injured person unless they are in immediate danger (like a burning vehicle). Moving them can worsen spinal or internal injuries.
Study focusApply safe loading, separation, parking, routing, and emergency-response decisions for hazmat.
Common trapChoosing a convenient action instead of the action that protects people and isolates the hazard.
Question 40
How can you tell if the road is becoming slippery due to dropping temperatures?
Mirrors and antennas are exposed to the cold air and will freeze before the road surface. If ice forms on them, be prepared for black ice on the road.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 41
Why is it important to shift gears correctly?
Correct shifting ensures you have engine braking when needed and prevents stalling or getting stuck in neutral, which compromises your control of the vehicle.
Study focusUse inspection habits to catch unsafe defects before driving.
Common trapChecking only obvious items and missing brake, tire, coupling, or defect-report steps.
Question 42
What should you do if your headlights fail while driving at night?
If headlights fail, immediately turn on hazard lights or turn signals to make yourself visible, slow down, and steer to a safe stop off the roadway.
Study focusUse inspection habits to catch unsafe defects before driving.
Common trapChecking only obvious items and missing brake, tire, coupling, or defect-report steps.
Question 43
When exiting a highway, when should you start slowing down?
You should maintain highway speed until you are in the deceleration lane, then brake to slow down to the posted ramp speed before entering the curve.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 44
What is the primary danger of driving through deep puddles of water?
Driving through deep water can soak the brake linings. Wet brakes can be weak, apply unevenly, or grab, leading to a lack of braking power or a skid.
Study focusRespond safely to hazards, emergencies, traction loss, and unsafe conditions.
Common trapReacting late or using sudden braking/steering when controlled action is safer.
Question 45
How do you dry wet brakes after driving through deep water?
To dry wet brakes, slow down, put the truck in a low gear, and lightly apply the brakes for a short distance. The friction generates heat which dries the linings.
Study focusApply core CDL safe-driving rules to common road and vehicle situations.
Common trapMemorizing rules without applying them to driving scenarios.
Question 46
Which of these is true about proper mirror adjustment?
Mirrors should be adjusted prior to starting the trip so you can see a small portion of your vehicle's side as a reference point to judge where other objects are.
Study focusChoose safe speed, spacing, and visual search habits for commercial vehicles.
Common trapDriving at passenger-car speeds without accounting for weight, space, weather, or grade.
Question 47
What is a 'pull-up' when backing a commercial vehicle?
A pull-up is when you pull forward during a backing maneuver to correct your angle or clear an obstacle. You should use as many pull-ups as necessary to back safely.
Study focusUse safe backing, turning, and basic-control habits.
Common trapBacking without a helper or failing to stop when visibility is uncertain.
Question 48
What is the danger of a loose tie-down on your cargo?
Loose tie-downs allow cargo to shift. A sudden shift in weight can destabilize the vehicle, leading to loss of steering control or a rollover.
Study focusControl off-tracking, rollover, rearward amplification, and trailer movement risks.
Common trapTurning or steering too sharply without accounting for trailer movement.
Question 49
How often should you inspect your tires during a trip in very hot weather?
In very hot weather, tires can overheat and catch fire or blow out. You must inspect them every 2 hours or 100 miles to ensure they are not too hot to touch.
Study focusApply safe loading, separation, parking, routing, and emergency-response decisions for hazmat.
Common trapChoosing a convenient action instead of the action that protects people and isolates the hazard.
Question 50
What should you do if your steering feels heavy or the vehicle pulls to one side?
Heavy steering or pulling to one side is a strong indicator of a front tire blowout or severe under-inflation. You must stop safely and inspect the tires immediately.
Study focusUse pre-trip inspection habits to identify unsafe vehicle-system defects before driving.
Common trapMemorizing a walk-around order without understanding which defects make the vehicle unsafe.
Question 51
You are approaching a railroad crossing in a heavy commercial vehicle. What is the safest general habit?
Railroad crossings require early observation and enough space beyond the tracks. A commercial vehicle should not enter unless it can clear the crossing safely.