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Free Practice Questions for Cambodia Heavy Vehicle Driving Test

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Sample Cambodia Heavy Vehicle Driving Test Practice Questions

Try these sample questions to review concepts for the Cambodia Heavy Vehicle Driving Test exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What is the primary function of the air compressor governor in a commercial vehicle's dual pneumatic brake system?
A.It controls when the air compressor pumps air into the storage reservoirs, cutting in at minimum pressure and cutting out at maximum pressure
B.It regulates the speed of the diesel engine when traveling downhill using compression braking
C.It automatically balances the hydraulic fluid levels between the front and rear brake circuits
D.It measures the gross axle weight on the drive axle and transmits the data to the tachograph
Explanation: A typical dual-circuit air-brake governor stops compressor pumping at cut-out pressure (often about 8–9 bar / 120–130 psi) and restarts pumping at cut-in pressure (often about 7 bar / 100 psi). Those figures are ordinary pneumatic-system practice, not a Cambodia-specific statutory table.
2If the low-air warning buzzer and lamp activate while you are driving a heavy vehicle with a dual-circuit pneumatic brake system, what should you do first?
A.Bring the vehicle to a safe stop as soon as possible because remaining air may be insufficient for normal braking
B.Increase engine speed and continue at highway speed so the compressor can catch up
C.Ignore the warning if the parking brake still releases
D.Shift to a higher gear to reduce compressor load
Explanation: A low-air warning means reservoir pressure is falling toward the point where service brakes weaken and spring brakes may apply. The safe response is to stop off the travelled way while control remains. Typical governors cut in around 7 bar and cut out around 8–9 bar; treat the warning as an immediate stop request, not a Cambodian-specific psi statute.
3Why must condensate be drained from air-brake reservoirs at the interval specified for the vehicle?
A.To expel accumulated water and compressor oil sludge that cause valve corrosion and brake failure
B.To completely depressurize the system so the tyres do not over-inflate overnight
C.To lubricate the brake lining drums with atomized oil vapors
D.To test whether the emergency spring brakes release smoothly under zero pressure
Explanation: Compressed air can carry moisture and compressor oil into reservoirs. Manual drains, where fitted, must be used at the manufacturer or fleet-maintenance interval; automatic dryers and drains change the procedure, so 'daily' is not a universal legal rule.
4What can occur if an air-brake system loses enough pressure to reach the spring-brake application range?
A.The emergency spring brakes automatically apply, locking the wheels mechanically to stop the vehicle
B.The engine automatically accelerates to force the alternator to generate auxiliary vacuum
C.The front steering axle brakes disengage to allow free steering into the ditch
D.The transmission automatically downshifts into first gear without clutch actuation
Explanation: Spring parking brakes are held released by air. At critically low pressure they begin to apply, so a low-air warning requires a controlled stop before braking control deteriorates. The exact application pressure is vehicle-specific, not a Cambodian 20-to-30-psi statute.
5What is 'brake lag' in a commercial vehicle equipped with an air brake system?
A.The physical delay (about 0.4 seconds) required for air to flow through the lines and actuate the brake shoes after the pedal is pressed
B.The delay in engine deceleration caused by high-viscosity synthetic engine oil
C.The interval between shifting gears in a non-synchronized manual transmission
D.The thermal recovery time required after brake linings overheat on a descent
Explanation: Unlike hydraulic fluid which is incompressible and transmits force instantaneously, compressed air takes about 0.4 to 0.5 seconds to travel through pneumatic tubing to the brake chambers. At 80 km/h, brake lag adds roughly 10 meters to total stopping distance.
6What causes 'brake fade' on a heavy truck or commercial bus descending a long mountain pass in Cambodia?
A.Excessive heat buildup from prolonged friction, reducing the friction coefficient between brake linings and drums
B.Air compressor over-pressurizing the reservoirs and bursting the diaphragm seals
C.Moisture freezing in the pneumatic lines during tropical rain showers
D.Engine oil leaking into the differential gear casing
Explanation: Repeated or continuous application of service brakes on steep downgrades generates extreme friction heat. As brake drums expand away from linings and friction material glazes, braking power fades dramatically, potentially leading to total runaway.
7What is the proper driving technique to prevent brake fade when descending a steep mountain grade with a fully loaded heavy vehicle?
A.Select a low gear before starting the descent, utilize engine auxiliary brakes (exhaust brake/retarder), and use snub braking only as needed
B.Shift the transmission into neutral and pump the foot brake pedal rapidly every 5 seconds
C.Maintain a high gear and ride the service foot brake continuously down the entire descent
D.Turn off the engine ignition to use engine vacuum as an emergency stopping anchor
Explanation: Before beginning a descent, drivers must shift into a low gear that allows engine compression and auxiliary retarders to hold the vehicle at a safe speed. If speed creeps up, apply firm 'snub' braking to slow down 5-10 km/h below the target, then release.
8During a pre-trip inspection of an S-cam drum brake, what component must be checked for excessive travel (stroke) when the brakes are applied?
A.The brake chamber pushrod and slack adjuster
B.The steering drag link tie rod end
C.The fifth-wheel release pivot lever
D.The fuel injection pump governor linkage
Explanation: Brake chamber pushrod stroke must be inspected. If the pushrod moves too far (excessive stroke due to out-of-adjustment slack adjusters or worn linings), the mechanical advantage of the S-cam is lost and braking efficiency drops sharply.
9Before connecting tractor and trailer air lines, how should a driver identify the service and supply couplings?
A.Use the vehicle's labels, color coding, coupling shape, and manufacturer instructions, then verify brake operation
B.Connect the lines at random because check valves correct any reversal
C.Identify the supply line only by touching the hose after driving
D.Leave one line disconnected and rely on tractor brakes
Explanation: Color conventions vary across equipment and markets. A driver should follow the labels and manufacturer system identification, make clean secure connections, and confirm trailer service and emergency brake operation before moving.
10What visual check must be performed after coupling a tractor fifth-wheel to a semi-trailer kingpin?
A.Verify with a flashlight that the locking jaws have fully closed around the kingpin shank and the safety latch is engaged
B.Check that the kingpin rests on top of the closed fifth-wheel jaws
C.Confirm that there is at least a 2-centimeter air gap between the fifth-wheel plate and trailer apron
D.Ensure the landing gear legs remain touching the ground during coupling
Explanation: The driver must look into the rear of the fifth wheel with a flashlight to verify that the locking jaws are closed completely around the narrow shank of the kingpin, the release handle is in the locked position, and zero space exists between apron and plate.

About the Cambodia Heavy Vehicle Driving Test Exam

Cambodian commercial driving licences in Categories C, D, and E (ប័ណ្ណបើកបរប្រភេទ គ ឃ ង) are issued by MPWT. Category C covers goods vehicles over 3.5 tonnes that may tow a trailer not over 0.75 tonnes. Category D covers passenger vehicles: D1 for 10–20 occupants including the driver and D2 for more than 20. Category E covers B, C, or D combinations with a trailer over 0.75 tonnes (E(B), E(C), E(D)). Minimum ages are 22 for C and D1 and 24 for D2 and E. Validity is 5 years. MPWT does not publish the selectable sitting languages on its service page; this bank is independent OpenExamPrep English-language MCQ study of the published C/D/E rules, not an official translation and not a substitute for school training or the practical test.

Exam sponsor: Ministry of Public Works and Transport (MPWT / ក្រសួងសាធារណការ និងដឹកជញ្ជូន). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Registered driving-school certificate (Types C, D, and E), computerised theory, then practical steering. MPWT does not allow the Type A/B online-only application path for Type C and above. Holders of C, D, or E may later convert to a 10-year Category B licence but cannot convert to Category A, and cannot convert back to C/D/E after taking B. This resource is independent English MCQ study, not a practical-test simulation.

Time Limit

Not published on the official MPWT driver's license service page.

Passing Score

Not published on the official MPWT driver's license service page. Theory must be passed before the practical test.

Exam / Certification Fees

95,000 Riels for Categories C and D; 100,000 Riels for Category E (MPWT fee table). Duplicate/renewal of Types B–E is 30,000 Riels.

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

Official weight unpublished (25 practice questions)

Heavy Vehicle Technical Systems, Air Brakes, and Coupling

Pneumatic brake circuits, governors, warnings, spring brakes, and fifth-wheel coupling.

Official weight unpublished (25 practice questions)

Axle Load Regulations, Weight Limits, and Weighbridge Compliance

Current Law on Roads Article 26 axle and vehicle-combination caps, as amended in July 2026, used at Cambodian weighbridges.

Official weight unpublished (20 practice questions)

Commercial Road Rules, Speed Limits, and Expressway Transport

Right-lane rule for vehicles over 3.5 t, Sub-Decree 86, and expressway class speeds.

Official weight unpublished (15 practice questions)

Passenger Transport (Category D) and Load Safety

D1/D2 passenger limits, Art. 56 loading bans, and second-driver triggers.

Official weight unpublished (15 practice questions)

Defensive Driving, Blind Spots, and Emergency Maneuvers

Off-tracking, stopping distance, jackknife prevention, and emergency priority.

Preparing for the Cambodia Heavy Vehicle Driving Test Exam

What You Need to Know

  • Passing score: Not published on the official MPWT driver's license service page. Theory must be passed before the practical test.
  • Assessment: Registered driving-school certificate (Types C, D, and E), computerised theory, then practical steering. MPWT does not allow the Type A/B online-only application path for Type C and above. Holders of C, D, or E may later convert to a 10-year Category B licence but cannot convert to Category A, and cannot convert back to C/D/E after taking B. This resource is independent English MCQ study, not a practical-test simulation.
  • Time limit: Not published on the official MPWT driver's license service page.
  • Exam / certification fees: 95,000 Riels for Categories C and D; 100,000 Riels for Category E (MPWT fee table). Duplicate/renewal of Types B–E is 30,000 Riels. Official sources

Using Our Practice Resources

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  • Review every answer and explanation
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Cambodia Heavy Vehicle Driving Test: Suggested Study Strategy

1Use Law on Roads Article 26 as amended in July 2026: 6 t (steering axle, two wheels), 10 t (single axle, four wheels), 19 t (tandem group, eight wheels), 24 t (tridem group, 12 wheels), and the separate current limits for rigid and articulated combinations.
2Do not invent a two-year Category B waiting period for C. Article 41 requires holding B or D1, age 22, and MPWT requires a driving-school certificate.
3On the Phnom Penh–Sihanoukville Expressway, MPWT sets 60 km/h minimum, 100 km/h maximum for heavy vehicles without trailers, and 80 km/h maximum with trailers.
4Vehicles over 3.5 tonnes must keep to the right lane except when turning left or overtaking (Art. 10).

Frequently Asked Questions

What is the difference between Cambodian Categories C, D, and E?

Article 40: C is goods vehicles over 3.5 tonnes (trailer ≤0.75 t). D1 is 10–20 passengers including the driver; D2 is more than 20. E is a B, C, or D vehicle towing a trailer over 0.75 tonnes, split as E(B), E(C), and E(D).

What ages and prior licences are required?

MPWT and Article 41: 22 years for C and D1; 24 years for D2 and E. Sit C only if you already hold B or D1; sit D1 if you hold B; sit D2 if you hold B, C, or D; sit E if you hold B, C, D1, or D2. A registered driving-school certificate is also required.

How long is a C, D, or E licence valid?

Five years after examination (Article 42 and the MPWT FAQ). Category A and B examination licences are valid for 10 years. Holders of C, D, or E may convert to a 10-year B licence but cannot convert that B licence back to C, D, or E, and cannot convert C/D/E into A.

Is this practice bank an official MPWT exam or translation?

No. It is independent English-language multiple-choice study by OpenExamPrep for Categories C, D, and E together, matching MPWT's grouping of those types as the driving-school commercial path. It is not an official paper and not a substitute for school training or the practical test.