Commercial Driving Vehicle Operation — Questions and Answers
Question 1: What is the correct technique for downhill braking with a commercial vehicle?
- Ride the brakes continuously
- Apply brakes hard at the bottom of the hill
- Use a low gear and apply brakes in short intervals to keep speed safe (Correct answer)
- Coast in neutral to save fuel
Correct answer: Use a low gear and apply brakes in short intervals to keep speed safe
Using engine braking in a lower gear combined with intermittent brake application prevents brake fade from overheating, which is the leading cause of loss-of-control on downgrades.
Question 2: What is the recommended following distance for a commercial vehicle at highway speeds?
- 2 seconds
- 4 seconds
- 6-7 seconds or more (Correct answer)
- 10 seconds
Correct answer: 6-7 seconds or more
Commercial vehicles require significantly more stopping distance than passenger cars. A minimum following distance of 6-7 seconds is recommended at highway speeds.
Question 3: What is the 'stab braking' technique?
- Pressing the brake pedal once and holding it
- Applying brakes fully, releasing when wheels lock, then reapplying when wheels start rolling again (Correct answer)
- Tapping brakes rapidly
- Using the parking brake while moving
Correct answer: Applying brakes fully, releasing when wheels lock, then reapplying when wheels start rolling again
Stab braking involves full brake application until wheels approach lockup, then releasing and reapplying. This is used in vehicles without anti-lock brakes during emergency stops.
Question 4: What causes a jackknife in a tractor-trailer?
- Turning the steering wheel too slowly
- The drive wheels losing traction while the trailer pushes the tractor, causing it to swing around (Correct answer)
- Driving too slowly
- Using the engine brake in warm weather
Correct answer: The drive wheels losing traction while the trailer pushes the tractor, causing it to swing around
Jackknifing occurs when the drive wheels lock or lose traction, and the momentum of the heavy trailer pushes the tractor sideways, creating a V-shape between tractor and trailer.
Question 5: What is the proper procedure for entering a curve with a commercial vehicle?
- Accelerate through the curve for stability
- Slow down BEFORE the curve and accelerate slightly through it (Correct answer)
- Brake hard while in the curve
- Maintain the same speed throughout
Correct answer: Slow down BEFORE the curve and accelerate slightly through it
Reducing speed before the curve prevents rollover risk from centrifugal force. Gentle acceleration through the curve helps maintain vehicle stability and traction.
Question 6: What is the danger of an overloaded commercial vehicle?
- It uses less fuel
- It can cause brake failure, tire blowouts, steering difficulty, and structural damage (Correct answer)
- It is only a legal problem
- Overloading makes the vehicle more stable
Correct answer: It can cause brake failure, tire blowouts, steering difficulty, and structural damage
Overloading puts excessive stress on brakes, tires, suspension, and steering systems, dramatically increasing the risk of equipment failure and loss of control.
Commercial Driving Vehicle Operation
What is the correct technique for downhill braking with a commercial vehicle?