If components are to be modified or fitted to a vehicle, the vehicle may only be driven on public roads if a valid type-approval has been granted for these vehicle parts. This applies, for example, to wheel rims, special wheels, auxiliary heaters, tow bars and many other extras. A number of requirements must be observed to ensure that the vehicle’s type approval is not invalidated.

For instance, modifications that affect the vehicle type, alterations that worsen exhaust emissions or increase noise levels, or changes that could endanger other road users will usually result in the vehicle’s type approval being revoked.

If the parts form a technical unit that can be treated independently in the type-approval process, the requirement for type-approval can be assessed. The type-approval may be restricted if the use of the parts can only be permitted on vehicles of a specific type, a specific model, or only where they are fitted or mounted in a specific manner. The validity of the type-approval may be made conditional upon inspection by an officially recognised expert or inspector for motor vehicle traffic or by a motor vehicle expert.

As a general rule, it is advisable to fit or install on vehicles only those parts for which there is a type-approval for vehicle parts in accordance with Section 22a of the Road Traffic Licensing Regulations (StVZO), a general operating licence for vehicle parts in accordance with Section 22 of the StVZO, or an equivalent approval based on EC Directives or ECE Regulations. Even in the case of parts for which a certificate exists, it may be necessary for the fitting or installation to be inspected and approved. Whether this is necessary can be determined from the part’s certificate. Furthermore, a type-approval for vehicle parts or the certificate must specify the vehicle types for which the part is suitable and how it is to be fitted. Many technical modifications must be recorded retrospectively by the registration authority in vehicle documents (Registration Certificate Part I, trailer register, etc.).

The registration authority may grant an individual type-approval to the authorised holder for vehicle parts that are not subject to the type-approval requirement under Section 22a of the Road Traffic Licensing Regulations, provided that- or installation inspection has been carried out by an officially recognised expert or inspector for motor vehicle traffic or by an officially recognised monitoring organisation, and whose use does not contravene any traffic regulations.