Exam Questions And Correct Answers

CDL Combination Tanker and Hazardous Materials (X) Endorsement Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of the anti-lock braking system (ABS) on a

combination vehicle?

• Increase fuel efficiency
• Prevent wheel lockup during braking
• Reduce tire wear
• Improve steering response

Rationale: ABS prevents wheel lockup, maintaining steering control

and reducing skidding during hard braking.

• When driving a tanker carrying hazardous materials, what is the

recommended following distance in ideal conditions?

• 1 second 1 / 4

• 2 seconds
• 3 seconds
• 4 seconds or more

Rationale: Longer following distances give extra time to react, which is

critical for tankers carrying hazardous materials.

• Which factor has the greatest effect on the rollover risk of a

combination vehicle?

• Engine power
• Tire pressure
• Liquid surge in a partially filled tanker
• Windshield size

Rationale: Partially filled tankers allow liquid to move, increasing

rollover risk due to shifting center of gravity.

• What is the most important reason to inspect the tanker’s baffles

before a trip?

• Ensure fuel efficiency
• Verify that liquid movement is controlled
• Check tire alignment
• Measure liquid temperature

Rationale: Baffles reduce liquid surge and improve vehicle stability.

• If a hazardous materials placard is missing or damaged during

transport, what should you do?

• Ignore it if the load seems safe 2 / 4

• Replace it with a temporary sign
• Do not transport until a proper placard is in place
• Notify the shipper after delivery

Rationale: Hazardous materials regulations require proper placarding

at all times to ensure safety and compliance.

6. When coupling a tractor to a semi-trailer, you should:

• Connect air lines first, then electrical lines
• Check kingpin engagement and locking jaws
• Fill trailer tanks before coupling
• Leave the trailer brakes disconnected

Rationale: Proper kingpin engagement ensures the trailer is securely

connected to prevent accidents.

• Which of the following is a primary hazard of driving a tanker on a

downgrade?

• Tire wear
• Engine overheating
• Loss of control due to liquid surge
• Increased fuel consumption

Rationale: Liquid movement and vehicle momentum on a downgrade

can cause swaying or loss of control.

• What is the main reason hazardous materials drivers must avoid

sudden starts and stops?

• Reduce engine wear 3 / 4

• Improve fuel economy
• Prevent liquid surge and load shift
• Extend tire life

Rationale: Sudden acceleration or braking can cause hazardous liquids

to shift, affecting stability.

• When inspecting a tanker trailer before a trip, which of the following is

essential?

• Check GPS function
• Inspect baffles, valves, and caps
• Verify interior lighting
• Clean the exterior paint

Rationale: Valves, baffles, and caps affect containment and safety of

liquid cargo.

• Which of these is a sign of a hazardous materials leak during

transport?

• Excessive tire vibration
• Unusual odors, hissing sounds, or visible liquid
• Headlight flickering
• Engine noise

Rationale: Leaks are often indicated by smell, sound, or visible signs

and require immediate action.

• What is the correct action if your tanker begins to skid on a

slippery surface?

• / 4