A dirt bike is ten times safer than a atv. 4 wheelers give a false sense of security of being stable. Tell your dad to give you a chance and find a friends bike and ride it in front of him. This way you can prove to him you are a capable rider. Anyone that thinks four wheelers is safer just ask my buddy who had his bottom half of his leg dislocated at his knee and tore every ligament in his knee. Anything can happen on either but you can get away from a dirtbike.