111+ Free LK DMT Heavy Vehicle Written Practice Questions

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2026 Statistics

Key Facts: LK DMT Heavy Vehicle Written Exam

Written Questions

DMT Sri Lanka

1 hour

Time Limit

DMT Sri Lanka

77%

Passing Mark

35/45 Correct Answers

2 years

Class B Required

DMT Regulations

20 years

Min Age

DMT Regulations

18 mos

Permit Validity

DMT Sri Lanka

The Sri Lanka DMT Heavy Vehicle Written Exam consists of 45 questions in a 1-hour time limit. It requires a passing score of 35 out of 45 (77%) and is administered by the Department of Motor Traffic (DMT). It covers the Highway Code, traffic signs, road markings, and heavy vehicle safety. A medical certificate from the NTMI and a 2-year Class B licence are prerequisites.

Sample LK DMT Heavy Vehicle Written Practice Questions

Try these sample questions to test your LK DMT Heavy Vehicle Written exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 111+ question experience with AI tutoring.

1At what air pressure should the low air pressure warning buzzer or light activate in a heavy vehicle equipped with air brakes?

A.Around 20 to 30 psi

B.Around 55 to 60 psi

C.Around 100 to 120 psi

D.Around 150 to 180 psi

Explanation: Heavy vehicles equipped with air brakes must have a low pressure warning device that activates when pressure drops below 55 to 60 psi. This warning alerts the driver to safely stop the vehicle before the brakes automatically lock up and lock wheels.

2Why must the air brake reservoir tanks on a heavy commercial lorry be drained daily by the driver?

A.To prevent the air pressure from escaping through the tires

B.To remove water and oil that can freeze or corrode the brake system

C.To adjust the tension of the brake pedal mechanism

D.To clean the internal air filter of the diesel engine

Explanation: Air compressors collect moisture and oil from the air, which accumulates at the bottom of the reservoir tanks. If not drained daily, this mixture can cause internal corrosion, clog valves, or freeze in cold weather, leading to complete brake failure.

3What is the primary safety function of a dual air brake system in a heavy passenger bus?

A.To double the braking power when descending steep hills

B.To provide separate front and rear brake circuits in case of a system leak

C.To allow the passenger bus to travel at higher speeds safely

D.To automate the parking brake release process during departures

Explanation: A dual air brake system has two separate air systems (primary and secondary) that share a single set of controls. If one system leaks or fails, the other system maintains enough braking capacity to bring the heavy vehicle to a safe stop.

4Under Sri Lankan Motor Traffic Regulations, what is the default maximum height allowed for a heavy lorry or bus, including its load?

A.2.8 meters

B.3.8 meters

C.4.6 meters

D.5.5 meters

Explanation: The default maximum legal height for a vehicle and its load in Sri Lanka is 3.8 meters. Exceeding this height requires a special permit from the Department of Motor Traffic and coordination with utility companies regarding overhead wires.

5What is the normal operating air pressure range for a heavy vehicle's air brake system?

A.20 to 40 psi

B.50 to 75 psi

C.85 to 120 psi

D.150 to 200 psi

Explanation: Normal air pressure in an air brake system is between 85 and 120 psi. The governor cut-out pressure stops the compressor from pumping at around 120 psi, and cut-in starts it when pressure drops to around 85-90 psi.

6What is the minimum legal tire tread depth required for a heavy lorry or motor coach in Sri Lanka?

A.0.8 mm

B.1.6 mm

C.3.0 mm

D.4.5 mm

Explanation: Sri Lankan road regulations mandate a minimum tire tread depth of 1.6 mm across the middle three-quarters of the tread. For heavy commercial vehicles carrying heavy loads or passengers, deeper tread is recommended for wet-weather traction.

7When draining moisture from the air brake tanks of a heavy lorry, which tank should be drained first?

A.The primary reservoir tank

B.The secondary reservoir tank

C.The wet tank (supply tank)

D.The emergency spring brake chamber tank

Explanation: The wet tank receives air directly from the compressor first and collects the most moisture and oil. Draining it first prevents excessive water from migrating downstream to the primary and secondary service tanks.

8During a pre-trip inspection of a heavy lorry, what indicates a critical leaf spring suspension defect?

A.Leaf springs are covered in road dust or light grime

B.More than one-fourth of the leaves in a spring stack are broken or shifted

C.The springs have a black coat of protective paint from the factory

D.The spring shackle bolts are tightly secured to the frame

Explanation: If a leaf spring stack has cracked, broken, or shifted leaves, or if more than one-fourth of the leaves are broken, the vehicle must be placed out of service. Driving with a compromised suspension poses a severe risk of vehicle rollover or axle separation.

9How should a heavy vehicle driver check the slack adjusters on an air brake system during a pre-trip inspection?

A.By visual inspection from the driver's cab while moving slowly

B.By releasing the parking brake, pulling hard on each slack adjuster, and checking for movement exceeding 1 inch

C.By pumping the brake pedal 20 times and checking if it gets stiff

D.By checking if the brake drums are hot to the touch when parked

Explanation: With the parking brake released and wheels chocked, a driver should pull the slack adjuster by hand or using a tool. If the pushrod moves more than about one inch where the rod attaches, the brake needs adjustment.

10What is the primary reason for performing a systematic, step-by-step pre-trip inspection of a heavy passenger bus?

A.To satisfy the operator's cleaning and washing requirements

B.To ensure the mechanical safety and roadworthiness of the bus before passengers board

C.To reduce the fuel consumption of the vehicle during the trip

D.To adjust the passenger seat belts and headrests

Explanation: A systematic pre-trip inspection ensures that all safety-critical components like brakes, steering, tires, suspension, lights, and emergency exits are checked. This prevents breakdowns and accidents, ensuring passenger safety.

About the LK DMT Heavy Vehicle Written Exam

The Sri Lanka Department of Motor Traffic (DMT) Heavy Vehicle Written Test is the mandatory first stage for obtaining a driving licence for passenger buses and heavy commercial transport trucks. The exam tests candidates on the Sri Lankan Highway Code, including traffic signs, road markings, priority rules, overtaking restrictions, speed limits, heavy vehicle operations, and mechanical knowledge.

Assessment

45 multiple-choice questions (MCQs)

Time Limit

1 hour

Passing Score

35 out of 45 correct answers (77%)

Exam Fee

Rs. 3,500 (DMT (Department of Motor Traffic, Sri Lanka))

LK DMT Heavy Vehicle Written Exam Content Outline

20%

Road Rules and Regulations

Drive-on-left rules, overtaking guidelines, speed limits for commercial vehicles, roundabout priorities, hill-driving priority, and merging traffic.

40%

Traffic Signs and Signals

Shapes and colors of warning, mandatory, regulatory, and information signs, road markings (solid/broken lines, box junctions), traffic light indicators, and police hand signals.

25%

Heavy Vehicle Safety and Controls

Safe following distances (three-second rule), air braking systems, cargo loading and weight distribution, blind spot safety (No-Zones), and defensive driving techniques.

10%

Driver Responsibilities & Law

Commercial logbooks and hours of service rules, driver documentation, permit rules, blood alcohol limits, and accident procedures.

Technical & Mechanical Knowledge

Pneumatic braking systems, diesel engine operation, tyre pressure, and basic commercial vehicle maintenance.

How to Pass the LK DMT Heavy Vehicle Written Exam

What You Need to Know

Passing score: 35 out of 45 correct answers (77%)
Assessment: 45 multiple-choice questions (MCQs)
Time limit: 1 hour
Exam fee: Rs. 3,500

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

LK DMT Heavy Vehicle Written Study Tips from Top Performers

1Pay attention to the specific speed limits for buses and heavy trucks, which are lower than private cars.

2Understand the mechanics of air brakes (dual air systems, low pressure warnings) compared to hydraulic brakes in light vehicles.

3Learn the Blind Spot rules (No-Zones) for trucks — side, front, and rear blind spots.

4Study RHD hand signals for turning left (clockwise rotation of right arm), turning right (straight arm), and slowing down.

5Know the commercial load limits and safe cargo securement regulations.

Frequently Asked Questions

What is the passing score for the Sri Lanka DMT heavy vehicle written test?

To pass the written test for a heavy vehicle licence, you must answer at least 35 out of 45 questions correctly (77%).

What are the eligibility requirements for the heavy vehicle test?

You must be at least 20 years old and have held a valid Class B (light vehicle) licence for at least 2 years. You also need a medical fitness certificate from the NTMI.

How long is the written test and how is it conducted?

The written test has a time limit of 1 hour (60 minutes). It is conducted as a computer-based examination using touch screens at most DMT regional offices, allowing you to see your results immediately.

What documents do I need to register for the exam?

You need your National Identity Card (NIC) or a valid passport, your existing Class B driving licence, a medical certificate issued by the National Transport Medical Institution (NTMI), and the required registration fees.

What is the speed limit for heavy vehicles in Sri Lanka?

For buses and trucks, the speed limit is lower than for passenger cars — typically 40 km/h in urban areas and 60 km/h on rural/provincial roads.