Theory for Category D (Buses)
This page presents the official Lithuanian Road Traffic Rules (KET) on the topic of "theory for category d", valid throughout the Republic of Lithuania under the 2026 rules. Understanding these provisions is essential for passing the theory exam at Regitra and for participating safely in traffic. Each provision below links to the official consolidated KET.
📚 Detailed rules
Category D1. Vehicles designed and constructed to carry no more than sixteen passengers, excluding the driver, and which are no more than 8 meters long; these vehicles may be coupled to trailers whose maximum permissible mass does not exceed 750 kg.
Category D1. The minimum age from which the right to drive may be obtained is 21 years, except for persons who, in the established manner, have obtained an initial professional qualification for the carriage of passengers.
Category D1E. Combinations of category D1 vehicles and trailers whose maximum permissible mass exceeds 750 kg.
Category D1E. The minimum age from which the right to drive may be obtained is 21 years, except for persons who, in the established manner, have obtained an initial professional qualification for the carriage of passengers.
Category D. Vehicles designed and constructed to carry more than eight passengers, excluding the driver; these vehicles may be coupled to a trailer whose maximum permissible mass does not exceed 750 kg.
Category D. The minimum age from which the right to drive may be obtained is 24 years, except for persons who, in the established manner, have obtained an initial professional qualification for the carriage of passengers.
Category DE. Combinations of category D vehicles and trailers whose maximum permissible mass exceeds 750 kg.
Category DE. The minimum age from which the right to drive may be obtained is 24 years, except for persons who, in the established manner, have obtained an initial professional qualification for the carriage of passengers.
Category T. Trolleybuses, that is, non-rail vehicles connected to an external electricity source.
Category T. The minimum age from which the right to drive may be obtained is 21 years.
A driver's license of categories B, C or D confers the right to drive respectively also category B1, C1 or D1 vehicles;
A driver's license of category C1E, CE, D1E or DE confers the right to drive also category BE vehicles;
A driver's license of category CE or DE confers the right to drive respectively also category C1E or D1E vehicles;
A driver's license of category CE confers the right to drive also category DE vehicles for drivers who have the right to drive category D vehicles.
Additional questions. Show how you will check whether all doors, including the cargo compartment, are reliably and securely closed.
Walking around the vehicle, check the doors – whether they are properly closed, not misaligned, and whether the hinges, handles and handle locks are in working order.
Additional questions. Show how you will check whether there are no leaks in the air system.
With the engine switched off, monitor whether the pressure in the system is not decreasing.
Additional questions. Explain what must be taken into account when loading the vehicle.
The weight and dimensions of the cargo must not exceed the permitted values. Distribute the cargo according to the permitted axle loads. Check whether the pallets are reliably wrapped in film. Arrange the cargo symmetrically; place heavier cargo at the bottom; secure it reliably. The cargo must not obstruct visibility, must not spill out, and must not pollute the environment.
Additional questions. Explain how you will check the condition of the reflectors.
Walking around the vehicle, check whether the reflectors are clean, not cracked, and properly reflect light.
Additional questions. Explain how you will check the condition of the windows.
Walking around the vehicle, check whether the windows are clean, not cracked, not scratched, and the glass units are not condensed.
Additional questions. Explain how you will check the condition of the mudguards.
Walking around the vehicle, check whether the mudguards are not torn off or torn.
Additional questions. Explain how you will check whether the air pressure in the tires is sufficient to drive safely.
Check the air pressure with a pressure gauge. By comparing the readings with the value recommended by the manufacturer, you will find out whether the air pressure in the tires is sufficient to drive safely.
Additional questions. Explain how you will check whether the tire tread depth is sufficient to drive safely.
You can measure the tire tread depth with a caliper or a special tool.
Additional questions. Explain how you will check whether the overall tire condition is suitable for safe driving.
The tires must be inspected; they must not be cracked, bulged, cut or otherwise damaged. The tread depth must correspond to the permitted minimum; tire wear must be even.
Additional questions. Explain how you will check the condition of the windshield wipers.
When fluid is sprayed, the wiper must clean the windshield evenly and cleanly. The wiper must not wobble on its arm, which would indicate a worn mounting.
Additional questions. Explain how you will check whether the body condition is suitable for safe driving.
Walking around the vehicle, check whether the body is not rusted, rotted, or broken, and whether the bolts are not unscrewed.
Additional questions. Show how you will check whether the air pressure in the brake system is suitable for safe driving.
Check the pressure gauge readings with the vehicle running. Normally, the pressure in the system should be about 125 psi (8.5 atmospheres). With the engine switched off, chock the wheels, release the parking brake, press the service brake, and monitor whether the pressure does not drop faster than 3 psi (0.2 atm) per minute in a vehicle, or 4 psi (0.3 atm) per minute in a vehicle combination.
With the ignition switched on, by pressing the brake pedal, release air from the system and monitor whether the warning signal (lamp) activates when the pressure drops to 60 psi (4 atm).
Continuing to release air, monitor whether the parking brake valve closes when the pressure drops to 40 psi (2.7 atm).
Additional questions. Show where you will check the oil level in the engine.
The engine oil level is checked with a brightly colored oil dipstick located next to the engine block.
Additional questions. Explain how you will determine whether the oil level in the engine is sufficient.
The vehicle is parked on level ground; the oil is checked when the engine is cold. Pull out the oil level dipstick, wipe it with a cloth, insert it back into its tube all the way and pull it out again. The oil level should be between the MIN and MAX marks.
Additional questions. Show how you will check whether the wheel mounting nuts are reliably tightened.
Walking around the vehicle, check the wheel nuts with a wrench.
Additional questions. Explain how you will check the suspension condition.
The condition of the suspension is periodically checked at a service center. Visually check whether the springs or leaf springs are not broken, and whether the air bags are not damaged. When driving, attention must be paid to any unusual sounds.
Additional questions. Explain how you will check whether the brake light signals work.
Use a helper who will check whether the brake light signals work when you press the brake pedal.
Additional questions. Show where you will check the fluid level in the engine cooling system.
Find and show the coolant expansion tank.
Additional questions. Explain how you will determine that the coolant level is sufficient.
There are MIN and MAX marks on the coolant tank. The coolant should not be more than MAX or less than MIN.
Additional questions. Show how you will check whether all the lights work.
When one of the lights burns out, a warning lamp may light up. Switch on the lights one by one and, walking around the vehicle, check them.
Additional questions. Show how the disk or card is replaced.
Show how you will replace the mechanical tachograph disk.
Additional questions. Explain how you will operate the lifting platform (only for vehicles with a lifting platform).
In the cabin, switch on the control panel; then operate the platform with the levers or buttons.
Additional questions. Show or explain how you will check whether the power steering works.
After starting the vehicle's engine, the steering wheel can be turned more easily than before starting the vehicle. This means that the power steering works.
Additional questions. Show how you will check whether the turn signals work.
For the turn signals to work, the ignition must be switched on. With the turn signals switched on, walk around the vehicle and check whether the turn signals on both sides work.
Additional questions. Show where the windshield washer fluid reservoir (container) is located.
Find and show the windshield washer fluid tank.
Additional questions. Explain how you will check the windshield washer fluid level.
The windshield washer fluid reservoir (container) is transparent, so you will check visually. There are MIN and MAX marks on the windshield washer fluid reservoir; the washer fluid should not be more than MAX or less than MIN. A lamp on the instrument panel may also signal that the fluid has run out.
Additional questions. Show which instrument readings you must check before starting the engine.
On the dashboard, monitor the glow plug indicator – it should go off; the pressure gauge, oil level indicator, and fuel gauge.
Additional questions. Show which instrument readings you must check after starting the engine.
On the dashboard, monitor the air pressure, oil pressure, and temperature indicators, the voltmeter. Pay attention to whether any malfunction indicator lamps are illuminated.
Lengths:
The maximum length of motor vehicles, except buses, trailers and combinations of motor vehicles, except buses, with trailers may be exceeded by 15 cm when they carry out intermodal transport operations.
Widths:
Height:
The technical parameters of heavy goods vehicles, buses and their combinations must be such that these vehicles can travel in a circle with an outer radius of 12.50 m and an inner radius of 5.30 m.
Additional requirements apply to buses:8.1. if the bus is stationary and its steered wheels are turned so that, when the bus moves, its outermost outer point can trace a circle with a radius of 12.50 m, the vertical plane tangent to the bus on the outside of the circle is determined by drawing a line on the ground; if it is an articulated bus, its stationary parts must be arranged along that plane;8.2. if the bus moves from a straight line into the area of the circle described in subparagraph 8.1, it must not protrude beyond the limits of this vertical plane by more than 0.60 m.
The maximum distance from the kingpin of the semi-trailer to the rear outer point of the semi-trailer is 12.00 m.
The maximum distance from the kingpin of a semi-trailer used in an intermodal transport operation to the rear outer point of the semi-trailer is 12.15 m.
The maximum distance from the front outer point of the cargo compartment of a heavy goods vehicle coupled with a trailer to the rear outer point of the trailer, minus the distance between the rear outer point of the heavy goods vehicle's cargo compartment and the front outer point of the trailer, is 15.65 m.
The maximum distance from the front outer point of the cargo compartment of a heavy goods vehicle coupled with a trailer to the rear outer point of the trailer is 16.40 m.
The distance between the rear axle of a heavy goods vehicle coupled with a trailer and the front axle of the trailer must be no less than 3 m.
The distance from the kingpin of a semi-trailer to any front point of the semi-trailer, measured in the horizontal plane, must not exceed 2.04 m.
Heavy goods vehicles:
The maximum permissible mass of a heavy goods vehicle having four or more axles, expressed in tons, must not exceed by more than five times the distance, expressed in meters, between the foremost and rearmost individual axles (not axle groups) of the heavy goods vehicle.
Buses:
Trailers: