When are safety decals required to be displayed on vehicles?

Safety decals are required to be displayed on vehicles after they have passed a safety inspection. This is crucial because safety inspections ensure that the vehicle meets the minimum safety standards set by the state. Once a vehicle has successfully passed this inspection, the display of the safety decal serves as an indicator that the vehicle is safe to operate. It informs both the operator and other road users that the vehicle has been verified for compliance with safety regulations, thus promoting road safety.

The other options do not align with the regulatory requirements. Simply purchasing a vehicle does not necessitate the immediate display of safety decals, as the vehicle may not yet meet safety standards. Registration alone is also not sufficient, as a vehicle could be registered without having undergone an inspection. Additionally, safety decals are not required after every use, as they indicate compliance with safety standards following an inspection rather than a usage condition.