# 2026 CDL General Knowledge Test – Actual Questions with Correct Answers & Rationales | (100%
Guarantee Pass)
Welcome to this comprehensive CDL General Knowledge Test review for 2026. This resource contains 250
actual-style questions covering all topics tested on the Commercial Driver’s License General Knowledge
exam: vehicle inspection, basic control, space management, hazard perception, night driving, emergency
procedures, cargo securement, air brakes, combination vehicles, railroad crossings, and federal regulations.
Each question includes the correct answer (in italics) and a short rationale. Use this exam to prepare for your
CDL permit test and strengthen your commercial driving knowledge.
Key Topics Covered
• Vehicle Inspection – Pre-trip inspection, emergency equipment, cargo securement checks, tire tread
depth, brake system checks
• Basic Control & Space Management – Following distance calculations, speed management, stopping
distance, lane positioning, turning techniques
• Hazard Perception & Emergency Procedures – Hydroplaning, skid recovery, brake failure, engine fires,
railroad crossing emergencies, escape ramps
• Night Driving & Adverse Conditions – Headlight use, glare recovery, black ice, wet/icy road braking, fog
driving
• Cargo Securement – Load distribution, center of gravity, tiedown requirements, cargo inspection
intervals
• Air Brakes – Governor cut-in/cut-out pressures, low air warning, spring brake engagement, air loss rates,
brake lag
• Combination Vehicles – Coupling/uncoupling, trailer swing, jackknife prevention, off-tracking
• Federal Regulations – BAC limits, DUI consequences, out-of-service orders, traffic violation reporting,
railroad crossing violations
,• Safe Driving Practices – Distracted driving prevention, communication with other drivers, tailgating
response, construction zone safety
Questions 1–250
1. You are driving a 50-foot truck at 50 mph on a dry road. What is your minimum following distance?
A) 5 seconds
B) 6 seconds
C) 7 seconds
D) 8 seconds
Answer B: 6 seconds
Rationale: The formula is 1 second for every 10 feet of vehicle length (50/10 = 5 seconds), plus 1 additional
second for speeds over 40 mph. Total = 6 seconds.
2. The center of gravity of a load should be:
A) Distributed evenly across all axles
B) Kept as low as possible
C) Concentrated near the rear of the trailer
D) Concentrated near the front of the trailer
Answer B: Kept as low as possible
Rationale: A high center of gravity makes the truck more likely to tip over during curves, turns, and sudden
lane changes. Keep heavy items on the floor and lighter items on top.
3. Retarders (Jake Brakes) should be used on slippery roads.
A) True
B) False
Answer B: False
Rationale: Retarders apply braking force to the drive wheels only. On wet, icy, or snow-covered roads, this
extra braking force can cause the drive wheels to lock up and induce a trailer jackknife. Turn retarders off in
slippery conditions.
4. How far ahead should you look while driving on the highway?
A) 5 to 8 seconds
,B) 12 to 15 seconds
C) 20 to 25 seconds
D) 30 to 35 seconds
Answer B: 12 to 15 seconds
Rationale: At highway speeds, 12 to 15 seconds equals approximately a quarter mile. Scanning this far
ahead gives you time to identify slowdowns, debris, or lane closures before they become emergencies.
5. If you are stopped at a rest area and found to have a BAC of 0.02% while in a CMV:
A) Nothing happens—it is below the legal limit
B) You will be placed Out-of-Service for 24 hours
C) You will receive a warning ticket
D) You will lose your CDL for 1 year
Answer B: You will be placed Out-of-Service for 24 hours
Rationale: The DUI limit for commercial drivers is 0.04%, but the zero-tolerance safety threshold is 0.02%.
At 0.02%, you are placed Out-of-Service for 24 hours. At 0.04% or above, you face a 1-year CDL
disqualification.
6. You should use your turn signals:
A) Only when other vehicles are visible
B) Early, continuously, and before every turn or lane change
C) Only when changing lanes
D) Only when turning
Answer B: Early, continuously, and before every turn or lane change
Rationale: Signal early and continuously to communicate your intentions to other motorists.
7. When a vehicle's engine stalls on a railroad track and you cannot restart it, you should:
A) Stay in the vehicle and call for help
B) Get everyone out and far away from the tracks, then call 911
C) Push the vehicle off the tracks immediately
D) Flag down the train with a white cloth
Answer B: Get everyone out and far away from the tracks, then call 911
Rationale: If your vehicle stalls on a railroad track, evacuate everyone immediately and move far away from
the tracks, then call for help.
, 8. The minimum tread depth for the front tires of a commercial vehicle is:
A) 2/32 inch
B) 4/32 inch
C) 6/32 inch
D) 8/32 inch
Answer B: 4/32 inch
Rationale: The minimum legal tread depth on steering (front) tires is 4/32 inch.
9. The minimum tread depth for drive and trailer tires is:
A) 2/32 inch
B) 4/32 inch
C) 6/32 inch
D) 8/32 inch
Answer A: 2/32 inch
Rationale: The minimum legal tread depth on drive and trailer tires is 2/32 inch.
10. What is the best way to stop on a wet or icy road?
A) Apply steady, firm pressure to brakes
B) Pump brakes rapidly
C) Use engine braking only
D) Brake normally, but start earlier and more gently
Answer D: Brake normally, but start earlier and more gently
Rationale: On wet or icy roads, brake earlier and more gently to avoid skidding.
11. You are driving a 30-foot straight truck at 55 mph. How much space should you keep between you
and the vehicle ahead?
A) 2 seconds
B) 3 seconds
C) 4 seconds
D) 5 seconds
Answer C: 4 seconds
Guarantee Pass)
Welcome to this comprehensive CDL General Knowledge Test review for 2026. This resource contains 250
actual-style questions covering all topics tested on the Commercial Driver’s License General Knowledge
exam: vehicle inspection, basic control, space management, hazard perception, night driving, emergency
procedures, cargo securement, air brakes, combination vehicles, railroad crossings, and federal regulations.
Each question includes the correct answer (in italics) and a short rationale. Use this exam to prepare for your
CDL permit test and strengthen your commercial driving knowledge.
Key Topics Covered
• Vehicle Inspection – Pre-trip inspection, emergency equipment, cargo securement checks, tire tread
depth, brake system checks
• Basic Control & Space Management – Following distance calculations, speed management, stopping
distance, lane positioning, turning techniques
• Hazard Perception & Emergency Procedures – Hydroplaning, skid recovery, brake failure, engine fires,
railroad crossing emergencies, escape ramps
• Night Driving & Adverse Conditions – Headlight use, glare recovery, black ice, wet/icy road braking, fog
driving
• Cargo Securement – Load distribution, center of gravity, tiedown requirements, cargo inspection
intervals
• Air Brakes – Governor cut-in/cut-out pressures, low air warning, spring brake engagement, air loss rates,
brake lag
• Combination Vehicles – Coupling/uncoupling, trailer swing, jackknife prevention, off-tracking
• Federal Regulations – BAC limits, DUI consequences, out-of-service orders, traffic violation reporting,
railroad crossing violations
,• Safe Driving Practices – Distracted driving prevention, communication with other drivers, tailgating
response, construction zone safety
Questions 1–250
1. You are driving a 50-foot truck at 50 mph on a dry road. What is your minimum following distance?
A) 5 seconds
B) 6 seconds
C) 7 seconds
D) 8 seconds
Answer B: 6 seconds
Rationale: The formula is 1 second for every 10 feet of vehicle length (50/10 = 5 seconds), plus 1 additional
second for speeds over 40 mph. Total = 6 seconds.
2. The center of gravity of a load should be:
A) Distributed evenly across all axles
B) Kept as low as possible
C) Concentrated near the rear of the trailer
D) Concentrated near the front of the trailer
Answer B: Kept as low as possible
Rationale: A high center of gravity makes the truck more likely to tip over during curves, turns, and sudden
lane changes. Keep heavy items on the floor and lighter items on top.
3. Retarders (Jake Brakes) should be used on slippery roads.
A) True
B) False
Answer B: False
Rationale: Retarders apply braking force to the drive wheels only. On wet, icy, or snow-covered roads, this
extra braking force can cause the drive wheels to lock up and induce a trailer jackknife. Turn retarders off in
slippery conditions.
4. How far ahead should you look while driving on the highway?
A) 5 to 8 seconds
,B) 12 to 15 seconds
C) 20 to 25 seconds
D) 30 to 35 seconds
Answer B: 12 to 15 seconds
Rationale: At highway speeds, 12 to 15 seconds equals approximately a quarter mile. Scanning this far
ahead gives you time to identify slowdowns, debris, or lane closures before they become emergencies.
5. If you are stopped at a rest area and found to have a BAC of 0.02% while in a CMV:
A) Nothing happens—it is below the legal limit
B) You will be placed Out-of-Service for 24 hours
C) You will receive a warning ticket
D) You will lose your CDL for 1 year
Answer B: You will be placed Out-of-Service for 24 hours
Rationale: The DUI limit for commercial drivers is 0.04%, but the zero-tolerance safety threshold is 0.02%.
At 0.02%, you are placed Out-of-Service for 24 hours. At 0.04% or above, you face a 1-year CDL
disqualification.
6. You should use your turn signals:
A) Only when other vehicles are visible
B) Early, continuously, and before every turn or lane change
C) Only when changing lanes
D) Only when turning
Answer B: Early, continuously, and before every turn or lane change
Rationale: Signal early and continuously to communicate your intentions to other motorists.
7. When a vehicle's engine stalls on a railroad track and you cannot restart it, you should:
A) Stay in the vehicle and call for help
B) Get everyone out and far away from the tracks, then call 911
C) Push the vehicle off the tracks immediately
D) Flag down the train with a white cloth
Answer B: Get everyone out and far away from the tracks, then call 911
Rationale: If your vehicle stalls on a railroad track, evacuate everyone immediately and move far away from
the tracks, then call for help.
, 8. The minimum tread depth for the front tires of a commercial vehicle is:
A) 2/32 inch
B) 4/32 inch
C) 6/32 inch
D) 8/32 inch
Answer B: 4/32 inch
Rationale: The minimum legal tread depth on steering (front) tires is 4/32 inch.
9. The minimum tread depth for drive and trailer tires is:
A) 2/32 inch
B) 4/32 inch
C) 6/32 inch
D) 8/32 inch
Answer A: 2/32 inch
Rationale: The minimum legal tread depth on drive and trailer tires is 2/32 inch.
10. What is the best way to stop on a wet or icy road?
A) Apply steady, firm pressure to brakes
B) Pump brakes rapidly
C) Use engine braking only
D) Brake normally, but start earlier and more gently
Answer D: Brake normally, but start earlier and more gently
Rationale: On wet or icy roads, brake earlier and more gently to avoid skidding.
11. You are driving a 30-foot straight truck at 55 mph. How much space should you keep between you
and the vehicle ahead?
A) 2 seconds
B) 3 seconds
C) 4 seconds
D) 5 seconds
Answer C: 4 seconds
