PHMSA is issuing this advisory bulletin to all owners and operators (operators) of hazardous liquid, carbon dioxide, and gas pipelines, as defined in 49 Code of Federal Regulations Parts 192 and 195, to clarify the regulatory requirements that may vary depending on the operational status of a pipeline. Further, this advisory bulletin identifies regulatory requirements operators must follow for the abandonment of pipelines. Pipeline owners and operators should verify their operations and procedures align with the regulatory intent of defined terms as described under this bulletin. Congress recognized the need for this clarification in its Protecting our Infrastructure of Pipelines and Enhancing Safety Act of 2016.