Terrorist incidents worldwide have highlighted the need for securing mass transit and passenger rail systems. The Transportation Security Admin. (TSA) is the primary fed. entity responsible for securing these systems. This report assesses: (1) the extent to which fed. and industry stakeholders have assessed risks to these systems since 2004, and how TSA has used this information to inform its security strategy; (2) key actions fed. and industry stakeholders have taken since 2004 and the extent to which fed. actions are consistent with TSA's security strategy, and the challenges TSA faces in implementing them; and (3) TSA's reported status in implementing 9/11 Commission Act provisions for mass transit and passenger rail security. Illus.