This final rule establishes standards for transporting portable tanks containing certain hazardous materials in container-on-flatcar (COFC) or trailer-on-flatcar (TOFC) service, without obtaining prior approval from the Federal Railroad Administration (FRA). Adoption of these standards as rules of general applicability will provide wider access to the benefits of transportation services that have been proven to be effective and safe. Persons holding approvals issued prior to this rulemaking who are unable to meet the standards established by this final rule will need to re-apply to the Associate Administrator for Safety FRA, prior to the expiration date stated in their current approval. The intended effects of this action are to reduce the need for obtaining written approval for certain COFC or TOFC services and to facilitate domestic and international commerce.