The 9/11 Act requires security training for employees of higher-risk freight railroad carriers, public transportation agencies (including rail mass transit and bus systems), passenger railroad carriers, and over-the-road bus (OTRB) companies. This final rule implements the regulatory mandate. Owner/operators of these higher-risk railroads, systems, and companies will be required to train employees performing security-sensitive functions, using a curriculum addressing preparedness and how to observe, assess, and respond to terrorist-related threats and/or incidents.  As part of this rulemaking, the Transportation Security Administration (TSA) is expanding its current requirements for rail security coordinators and reporting of significant security concerns (currently limited to freight railroads, passenger railroads, and the rail operations of public transportation systems) to include the bus components of higher-risk public transportation systems and higher-risk OTRB companies. TSA is also adding a definition for Transportation Security-Sensitive Materials (TSSM). Other provisions are being amended or added, as necessary, to implement these additional requirements.