A method of assembling a vehicle includes providing a mandrel that approximates the shape of a fuselage to be formed, winding a fiber around the mandrel by rotating the mandrel with a driver, heating the fiber to form the fuselage having a structural, hardened shell, removing the mandrel from the fuselage, and mounting the fuselage onto a frame rail of the vehicle. \u2014from 30% to 50% of one or more types of plasticizers, at least one of which is polymeric in nature, or is a heavy monomeric plasticizer, \u2014from 1% to 20% of additives, such as pigments or fillers, stabilizers, antioxidants, processing additives and lubricants. A degree-of-toner-deterioration calculation unit calculates the degree of toner deterioration on the basis of the variation in data of the toner adhesion amount at multiple places detected by the toner adhesion amount detection unit.