The Rail Transportation Security Final Rule, published in the Federal Register on November 26, 2008, added rail-related terms and covered persons to Part 1520, including railroad carriers, rail facilities, rail hazardous materials shippers and receivers, and rail transit systems that are detailed in a new Part 1580. Although rail vulnerability assessments and threat information were already SSI under Part 1520, this rail final rule specifies that information on rail security investigations and inspections, security measures, security training materials, critical rail infrastructure assets, and research and development is also SSI.