An assessment is required following modifications to your vehicle. When must this be performed?

In the context of German traffic regulations, any modifications made to a vehicle that affect its specifications, performance, or safety features typically require an assessment to ensure compliance with legal standards. This is important because changes could potentially affect the vehicle's safety on the road.

The correct approach is to have the assessment conducted promptly after any such modifications (choice 1), as it guarantees that the vehicle is still roadworthy and meets all required standards before being used again. While it’s also true that at the time of the next inspection (choice 2) or when demanded by the registration authority (choice 3) might lead to an assessment eventually, waiting for these scenarios could pose risks both legally and in terms of safety.

Therefore, having the assessment done promptly after the modifications ensures compliance and safety right away, which is why option 1 is crucial. The other two options do not suffice because they could delay necessary safety checks that should happen immediately following alterations.