Is it legally mandatory at a national level to obtain and display the DGT environmental sticker on your vehicle?
A)Yes, it is mandatory for all vehicles registered in Spain, and driving without it carries an automatic fine.
B)No, obtaining and displaying the sticker is voluntary nationwide, though individual municipalities can enforce their own mandatory rules to enter specific zones.Correct
C)It is only mandatory for heavy trucks and public transport vehicles, but completely optional for private passenger cars.
At the national DGT level, placing the sticker on the vehicle is voluntary. However, cities use them to manage Low Emission Zones (ZBE), meaning municipal regulations can effectively make them mandatory if you want to drive through restricted city centers.