Passenger rail systems are vital to the nation's transportation infrastructure, providing approximately 14 million passenger trips each weekday. Recent terrorist attacks on these systems around the world highlight the vulnerability of these systems. The Transportation Security Admin. is the primary federal entity responsible for securing passenger rail systems. This technology assessment reviewed: (1) the availability of explosives detection technologies and their ability to help secure the passenger rail environment; and (2) key operational and policy factors that impact the role of explosives detection technologies in the passenger rail environment. It analyzed test reports on various explosives detection technologies. Charts and tables.