; and (3) the feasibility of an operator of a natural gas distribution system implementing a pipeline safety management system described in paragraph (1) based on the size of the operator as measured by— (A) the number of customers the operator has; and (B) the amount of natural gas the operator transports. (b) Requirements As part of the report required under subsection (a), the Secretary shall provide guidance or recommendations that would further the adoption of safety management systems in accordance with the standard established by the American Petroleum Institute entitled Pipeline Safety Management System Requirements and numbered American Petroleum Institute Recommended Practice 1173. (c) Evaluation and promotion of safety management systems The Secretary and the relevant State authority with a certification in effect under section 60105 of title 49, United States Code, as applicable, shall— (1) promote and assess pipeline safety management systems frameworks developed by operators of natural gas distribution systems and described in the report under subsection (a), including— (A) if necessary, using independent third-party evaluators; and (B) through a system that promotes self-disclosure of— (i) errors; and (ii) deviations from regulatory standards; and (2) if a deviation from a regulatory standard is identified during the development and application of a pipeline safety management system, certify that— (A) due consideration will be given to factors such as flawed procedures, honest mistakes, or lack of understanding; and (B) the operators and regulators use the most appropriate tools to fix the deviation, return to compliance, and prevent the recurrence of the deviation, including— (i) root cause analysis