CDL Permit Practice Test

Q: What is the minimum tread depth for front tires on a commercial vehicle?

• 2/32 inch
• 4/32 inch (correct answer)
• 6/32 inch
• 8/32 inch

Explanation: Front tires must have at least 4/32 inch tread depth. Other tires need at least 2/32 inch. This ensures adequate traction and safety, especially in wet conditions.

Q: Which of these statements about backing a commercial vehicle is true?

• You should back and turn toward the driver's side whenever possible
• You should use a helper whenever possible (correct answer)
• It is safer to back to the right side of the vehicle than to the left
• Backing is always safe if you use caution

Explanation: You should always use a helper when backing if possible. Backing is one of the most dangerous maneuvers. If no helper is available, get out and check your clearance before backing.

Q: Controlled braking is used to:

• Apply maximum braking power without locking wheels (correct answer)
• Keep the vehicle in a straight line when braking
• Prevent brake fade on long downgrades
• All of the above

Explanation: Controlled braking means applying the brakes as hard as you can without locking the wheels. This gives you maximum stopping power while maintaining steering control.

Q: When driving a 60-foot vehicle at 55 mph, how much space should you keep in front of you?

• 3 seconds
• 5 seconds
• 6 seconds (correct answer)
• 8 seconds

Explanation: For vehicles over 40 feet or traveling above 40 mph, you should maintain at least 6 seconds of following distance. Add one second for each additional hazard like bad weather or heavy traffic.

Q: Cargo inspections should be performed:

• Within the first 50 miles of a trip
• Every 3 hours or 150 miles
• After every break during driving
• All of the above (correct answer)

Explanation: Federal regulations require cargo inspection within the first 50 miles, every 3 hours or 150 miles, and after every break. This ensures cargo hasn't shifted and remains secure.

Q: Which of these is NOT a good rule to follow when driving at night?

• Keep your speed slow enough to stop within the range of your headlights
• Use high beams when it is safe and legal to do so
• Look directly at oncoming headlights to judge the other vehicle's speed (correct answer)
• Avoid looking at bright lights for more than a second

Explanation: You should never look directly at oncoming headlights as this can temporarily blind you. Instead, look slightly to the right edge of your lane and use peripheral vision.

Q: Which of these statements about drinking alcohol is true?

• A few beers are safer than hard liquor
• Coffee and a shower will help you sober up faster
• Alcohol affects judgment and self-control, which are needed for safe driving (correct answer)
• If you eat while drinking, alcohol has less effect

Explanation: Alcohol impairs judgment and self-control, both critical for safe driving. No amount of coffee, food, or showers will speed up the elimination of alcohol from your system. Only time can do that.

Q: What is the primary function of the air compressor in an air brake system?

• To store compressed air for braking
• To pump air into the air storage tanks (correct answer)
• To release air from the brake chambers
• To monitor air pressure levels

Explanation: The air compressor pumps air into the air storage tanks to build and maintain system pressure. It's driven by the engine and is essential for maintaining the 100-125 psi operating pressure.