CDL 2026/2027 COMPREHENSIVE
PROFESSIONAL EXAMINATION
1. When conducting a pre-trip inspection, what is the maximum allowable play in a steering
wheel with a 20-inch diameter?
A. 1 inch
B. 3 inches
C. 2 inches
D. 4 inches
Answer: C
Conceptual Explanation: For a steering wheel with a 20-inch diameter, play of more than
10 degrees (approximately 2 inches) is considered unsafe.
2. Which of the following describes the ‘Total Stopping Distance’ formula?
A. Reaction Distance + Braking Distance
B. Perception Distance + Reaction Distance + Braking Distance
C. Perception Distance + Braking Distance
,D. Reaction Distance + Lag Distance + Braking Distance
Answer: B
Conceptual Explanation: Total stopping distance is the sum of perception distance,
reaction distance, and braking distance.
3. In a vehicle equipped with air brakes, what is the primary purpose of the ‘Alcohol
Evaporator’?
A. To cool the air before it enters the reservoir
B. To reduce the risk of ice in air brake valves during cold weather
C. To lubricate the air compressor piston
D. To filter out oil contaminants from the system
Answer: B
Conceptual Explanation: The alcohol evaporator puts alcohol into the air system to help
prevent ice from forming in air brake valves and lines during cold weather.
4. What is the minimum tread depth required for every major groove on a front tire of a
commercial motor vehicle?
A. 2/32 of an inch
B. 3/32 of an inch
C. 4/32 of an inch
D. 6/32 of an inch
, Answer: C
Conceptual Explanation: Federal regulations require a minimum tread depth of 4/32-inch
on all major grooves of front tires.
5. When driving a combination vehicle, ‘Off-tracking’ or ‘Cheating’ causes which part of the
vehicle to follow a tighter path?
A. The front wheels
B. The rear wheels
C. The steering axle
D. The fifth wheel connection
Answer: B
Conceptual Explanation: Off-tracking occurs when the rear wheels follow a shorter,
tighter path than the front wheels during a turn.
6. If your vehicle is equipped with an Antilock Braking System (ABS), how should you brake
during an emergency?
A. Apply full brakes and keep your foot on the pedal
B. Pump the brakes rapidly to prevent lockup
C. Use the stab braking method
D. Apply 50% pressure to avoid activating the system
Answer: A
PROFESSIONAL EXAMINATION
1. When conducting a pre-trip inspection, what is the maximum allowable play in a steering
wheel with a 20-inch diameter?
A. 1 inch
B. 3 inches
C. 2 inches
D. 4 inches
Answer: C
Conceptual Explanation: For a steering wheel with a 20-inch diameter, play of more than
10 degrees (approximately 2 inches) is considered unsafe.
2. Which of the following describes the ‘Total Stopping Distance’ formula?
A. Reaction Distance + Braking Distance
B. Perception Distance + Reaction Distance + Braking Distance
C. Perception Distance + Braking Distance
,D. Reaction Distance + Lag Distance + Braking Distance
Answer: B
Conceptual Explanation: Total stopping distance is the sum of perception distance,
reaction distance, and braking distance.
3. In a vehicle equipped with air brakes, what is the primary purpose of the ‘Alcohol
Evaporator’?
A. To cool the air before it enters the reservoir
B. To reduce the risk of ice in air brake valves during cold weather
C. To lubricate the air compressor piston
D. To filter out oil contaminants from the system
Answer: B
Conceptual Explanation: The alcohol evaporator puts alcohol into the air system to help
prevent ice from forming in air brake valves and lines during cold weather.
4. What is the minimum tread depth required for every major groove on a front tire of a
commercial motor vehicle?
A. 2/32 of an inch
B. 3/32 of an inch
C. 4/32 of an inch
D. 6/32 of an inch
, Answer: C
Conceptual Explanation: Federal regulations require a minimum tread depth of 4/32-inch
on all major grooves of front tires.
5. When driving a combination vehicle, ‘Off-tracking’ or ‘Cheating’ causes which part of the
vehicle to follow a tighter path?
A. The front wheels
B. The rear wheels
C. The steering axle
D. The fifth wheel connection
Answer: B
Conceptual Explanation: Off-tracking occurs when the rear wheels follow a shorter,
tighter path than the front wheels during a turn.
6. If your vehicle is equipped with an Antilock Braking System (ABS), how should you brake
during an emergency?
A. Apply full brakes and keep your foot on the pedal
B. Pump the brakes rapidly to prevent lockup
C. Use the stab braking method
D. Apply 50% pressure to avoid activating the system
Answer: A
