What alterations can result in the permit for use (Betriebserlaubnis) being cancelled?

In German traffic law, the permit for use (Betriebserlaubnis) can be cancelled if certain modifications are made to a vehicle without proper approval. Specifically, fitting a sidecar or fitting tyres of a different size than those approved can affect the vehicle's safety, stability, and handling, which is why these changes require official approval. Without this approval, the original permit is invalidated. On the other hand, fitting a rear fog lamp generally does not cancel the permit because it is considered an additional safety feature that complies with regulations when installed correctly. Understanding which alterations impact the vehicle's approved specifications helps ensure safety and legal compliance on the road.