Louisiana Commercial Driver License
Pre-Trip Exam Practice Questions And
Correct Answers (Verified Answers) Plus
1. During a pre-trip inspection of a tractor-trailer with a dual-circuit air brake system,
the driver observes that the low-air warning buzzer activates at 55 psi and the tractor
protection valve pops out at 45 psi. The governor cut-in is 100 psi and cut-out is 125
psi. Which conclusion is most accurate?
A. The system meets FMCSA requirements because the warning activates before the
protection valve.
B. The warning buzzer must activate by 60 psi and the tractor protection valve must pop
out between 20 and 45 psi, so these readings are compliant.
C. The low-air warning must activate before 55 psi and the tractor protection valve must
pop out between 20 and 45 psi; the warning is set too late.
D. The governor cut-in and cut-out pressures are out of specification, indicating a faulty
governor.
Answer: B. The warning buzzer must activate by 60 psi and the tractor protection
valve must pop out between 20 and 45 psi, so these readings are compliant.
Rationale: FMCSA requires the low-air warning to activate by 60 psi (not before 55 psi
specifically) and the tractor protection valve to pop out between 20 and 45 psi. The
observed values are within these ranges, so the system is compliant. Option C misstates the
warning threshold, while D incorrectly focuses on governor pressures that are normal.
Page 1 of 58
,2. A driver is inspecting a flatbed trailer loaded with steel coils. The coils are secured
with four tie-downs, each with a working load limit (WLL) of 4,000 lb. The cargo
weighs 15,000 lb. According to 49 CFR 393.110, what is the minimum number of
tie-downs required, and is this securement adequate?
A. Minimum 2 tie-downs; adequate because 4 provide redundancy.
B. Minimum 4 tie-downs; adequate because aggregate WLL exceeds cargo weight.
C. Minimum 4 tie-downs; inadequate because aggregate WLL must be at least 50% of
cargo weight, and 16,000 lb is less than 7,500 lb.
D. Minimum 4 tie-downs; adequate because each tie-down independently exceeds 50%
of cargo weight.
Answer: B. Minimum 4 tie-downs; adequate because aggregate WLL exceeds cargo
weight.
Rationale: For cargo over 10,000 lb, at least 4 tie-downs are required. The aggregate WLL
(4 × 4,000 = 16,000 lb) must be at least 50% of the cargo weight (7,500 lb), which it
exceeds. Thus, the securement is adequate; option C miscalculates the threshold.
Page 2 of 58
,3. Which of the following best explains why a driver must drain air tanks during a
pre-trip inspection, and what is the correct procedure?
A. To remove oil buildup; drain only the primary tank while the engine is off.
B. To remove moisture and contaminants; drain all tanks fully with system pressure at
maximum.
C. To test for leaks; drain tanks until pressure drops to 60 psi, then close valves.
D. To verify compressor operation; drain tanks while the engine is running at high idle.
Answer: B. To remove moisture and contaminants; drain all tanks fully with system
pressure at maximum.
Rationale: Air tanks accumulate moisture and oil, which can freeze or damage valves. The
correct procedure is to drain all tanks completely with the system at full pressure to expel
contaminants. Options A, C, and D describe incorrect or incomplete procedures.
4. During a pre-trip inspection, a driver notices that the fifth wheel locking jaws are
not completely closed around the kingpin. What is the most critical immediate action?
A. Apply a thin layer of grease to the fifth wheel plate and recheck.
B. Adjust the fifth wheel height and attempt to couple again.
C. Do not move the vehicle; the trailer is not securely coupled and must be re-coupled or
repaired.
D. Engage the tractor protection valve and proceed at low speed to the nearest shop.
Answer: C. Do not move the vehicle; the trailer is not securely coupled and must be
re-coupled or repaired.
Rationale: An improperly closed fifth wheel locking jaw indicates the kingpin is not
secured, risking trailer separation. The driver must not move the vehicle until it is properly
coupled. Options A, B, and D either ignore the safety hazard or suggest unsafe movement.
Page 3 of 58
, 5. A driver is inspecting a bus equipped with a hydraulic brake system. Which
component check is essential to verify proper brake fluid condition and level?
A. Check the master cylinder reservoir for fluid level and contamination.
B. Inspect the brake drums for cracks and discoloration.
C. Measure the slack adjuster travel on the rear brakes.
D. Test the air compressor cut-in pressure.
Answer: A. Check the master cylinder reservoir for fluid level and contamination.
Rationale: Hydraulic brake systems require checking the master cylinder fluid level and
condition. Options B and C are relevant to air brake or mechanical checks, and D is
specific to air brake systems, not hydraulic.
6. Which of the following is a required check for the steering system during a pre-trip
inspection?
A. Measure steering wheel free play with the engine off and front wheels straight.
B. Verify power steering fluid level and check for leaks.
C. Inspect the pitman arm and drag link for cracks or excessive play.
D. All of the above.
Answer: D. All of the above.
Rationale: A complete steering inspection includes checking free play, fluid level, and
steering linkage components. Each of A, B, and C is a required check, making D the correct
comprehensive answer.
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Pre-Trip Exam Practice Questions And
Correct Answers (Verified Answers) Plus
1. During a pre-trip inspection of a tractor-trailer with a dual-circuit air brake system,
the driver observes that the low-air warning buzzer activates at 55 psi and the tractor
protection valve pops out at 45 psi. The governor cut-in is 100 psi and cut-out is 125
psi. Which conclusion is most accurate?
A. The system meets FMCSA requirements because the warning activates before the
protection valve.
B. The warning buzzer must activate by 60 psi and the tractor protection valve must pop
out between 20 and 45 psi, so these readings are compliant.
C. The low-air warning must activate before 55 psi and the tractor protection valve must
pop out between 20 and 45 psi; the warning is set too late.
D. The governor cut-in and cut-out pressures are out of specification, indicating a faulty
governor.
Answer: B. The warning buzzer must activate by 60 psi and the tractor protection
valve must pop out between 20 and 45 psi, so these readings are compliant.
Rationale: FMCSA requires the low-air warning to activate by 60 psi (not before 55 psi
specifically) and the tractor protection valve to pop out between 20 and 45 psi. The
observed values are within these ranges, so the system is compliant. Option C misstates the
warning threshold, while D incorrectly focuses on governor pressures that are normal.
Page 1 of 58
,2. A driver is inspecting a flatbed trailer loaded with steel coils. The coils are secured
with four tie-downs, each with a working load limit (WLL) of 4,000 lb. The cargo
weighs 15,000 lb. According to 49 CFR 393.110, what is the minimum number of
tie-downs required, and is this securement adequate?
A. Minimum 2 tie-downs; adequate because 4 provide redundancy.
B. Minimum 4 tie-downs; adequate because aggregate WLL exceeds cargo weight.
C. Minimum 4 tie-downs; inadequate because aggregate WLL must be at least 50% of
cargo weight, and 16,000 lb is less than 7,500 lb.
D. Minimum 4 tie-downs; adequate because each tie-down independently exceeds 50%
of cargo weight.
Answer: B. Minimum 4 tie-downs; adequate because aggregate WLL exceeds cargo
weight.
Rationale: For cargo over 10,000 lb, at least 4 tie-downs are required. The aggregate WLL
(4 × 4,000 = 16,000 lb) must be at least 50% of the cargo weight (7,500 lb), which it
exceeds. Thus, the securement is adequate; option C miscalculates the threshold.
Page 2 of 58
,3. Which of the following best explains why a driver must drain air tanks during a
pre-trip inspection, and what is the correct procedure?
A. To remove oil buildup; drain only the primary tank while the engine is off.
B. To remove moisture and contaminants; drain all tanks fully with system pressure at
maximum.
C. To test for leaks; drain tanks until pressure drops to 60 psi, then close valves.
D. To verify compressor operation; drain tanks while the engine is running at high idle.
Answer: B. To remove moisture and contaminants; drain all tanks fully with system
pressure at maximum.
Rationale: Air tanks accumulate moisture and oil, which can freeze or damage valves. The
correct procedure is to drain all tanks completely with the system at full pressure to expel
contaminants. Options A, C, and D describe incorrect or incomplete procedures.
4. During a pre-trip inspection, a driver notices that the fifth wheel locking jaws are
not completely closed around the kingpin. What is the most critical immediate action?
A. Apply a thin layer of grease to the fifth wheel plate and recheck.
B. Adjust the fifth wheel height and attempt to couple again.
C. Do not move the vehicle; the trailer is not securely coupled and must be re-coupled or
repaired.
D. Engage the tractor protection valve and proceed at low speed to the nearest shop.
Answer: C. Do not move the vehicle; the trailer is not securely coupled and must be
re-coupled or repaired.
Rationale: An improperly closed fifth wheel locking jaw indicates the kingpin is not
secured, risking trailer separation. The driver must not move the vehicle until it is properly
coupled. Options A, B, and D either ignore the safety hazard or suggest unsafe movement.
Page 3 of 58
, 5. A driver is inspecting a bus equipped with a hydraulic brake system. Which
component check is essential to verify proper brake fluid condition and level?
A. Check the master cylinder reservoir for fluid level and contamination.
B. Inspect the brake drums for cracks and discoloration.
C. Measure the slack adjuster travel on the rear brakes.
D. Test the air compressor cut-in pressure.
Answer: A. Check the master cylinder reservoir for fluid level and contamination.
Rationale: Hydraulic brake systems require checking the master cylinder fluid level and
condition. Options B and C are relevant to air brake or mechanical checks, and D is
specific to air brake systems, not hydraulic.
6. Which of the following is a required check for the steering system during a pre-trip
inspection?
A. Measure steering wheel free play with the engine off and front wheels straight.
B. Verify power steering fluid level and check for leaks.
C. Inspect the pitman arm and drag link for cracks or excessive play.
D. All of the above.
Answer: D. All of the above.
Rationale: A complete steering inspection includes checking free play, fluid level, and
steering linkage components. Each of A, B, and C is a required check, making D the correct
comprehensive answer.
Page 4 of 58
