Certain technical modifications must be inspected immediately by the Technical Inspection Agency or an officially recognized inspection organization (DEKRA, GTÜ, KÜS, TÜV):

• Change in vehicle type

• Change in engine displacement or power output

• Increase in the maximum speed specified by the vehicle design

• Reduction of the maximum speed specified by the vehicle design, if this is relevant to the driver’s license or if tires with lower speed ratings are to be used

• Changes to the permissible axle loads, gross vehicle weight, payload, fifth-wheel load, trailer load, or towing capacity

• Increase in vehicle dimensions, except for passenger cars and motorcycles

• Changes to the number of seats, sleeping berths, or standing room in buses

• Changes to exhaust emissions or noise levels, provided they affect motor vehicle tax or traffic restrictions

These technical modifications must be recorded in the vehicle documents by the competent authority.