Car toll for Serviccar?

Hello everyone, I’ve got a question now, it’s about the toll that comes. I’ve read the motorcycle excepted, now my question, who knows if you can let the service car of hd as a motorcycle.that of my wife is approved as a car.I always thought that the type of registration has to do with the gauge width, now my in net has read,that it has to do with the type of construction.Who can enlighten me? Greetings and thanks for the answers Ingolf