585.1—Definitions.
        
        (b) 
         The terms bus, gross vehicle weight rating or GVWR, motor vehicle, multipurpose passenger vehicle, passenger car, and truck are used as defined in  § 571.3 of this chapter.
    
    
        
        (c) 
        
            Production year means the 12-month period between September 1 of one year and August 31 of the following year, inclusive, unless otherwise specified.