These general guidelines, based on ECE/TRANS/WP.29/1044/Rev.2, as amended by WP.29-182-11, provide guidance to subsidiary bodies of the World Forum for Harmonization of Vehicle Regulations on procedures for making and amending UN Regulations and drafting their scope, administrative provisions, alternative requirements and cross-references. The guidelines emphasize mutual recognition of UN type approvals and clarify that UN Regulations are optional for Contracting Parties. They address procedures for new UN Regulations, series of amendments, supplements, and corrigenda, with transitional provisions specifying dates when Contracting Parties must accept or may refuse approvals. Special procedures apply to UN Regulation No. 0 on International Whole Vehicle Type Approval, amended no more than once per year with Date (b) by default set at 1 September of the year following adoption.