PHMSA is considering revisions to the Hazardous Materials Regulations (HMR) to improve the regulations applicable to the transportation of hazardous materials by rail. The revisions are based on eight petitions received from the regulated community and four National Transportation Safety Board (NTSB) Recommendations which are referenced by a petition. In this ANPRM, we outline the petitions and NTSB recommendations, identify a preliminary estimate of costs and benefits from the petitions, pose several questions, and solicit comments and data from the public. Under Executive Order 13563, Federal agencies were asked to periodically review existing regulations. The questions posed in this ANPRM and responses by commenters will be used in conjunction with a retrospective review of existing requirements aimed to modify, streamline, expand, or repeal existing rules that are outmoded, ineffective, insufficient, or excessively burdensome.