The coordinated hijackings and deliberate crashes of airplanes into the World Trade Center in New York and the Pentagon in Washington, DC, on September 11, 2001, dramatically heightened both the perception and the reality of the threat terrorism poses to public transportation systems. Governments of countries that perceive an elevated level of threat are investing considerable resources to implement comprehensive programs to enhance security in all key modes of transportation, including aviation, maritime traffic, highways, and mass transit.
A systems-based approach to managing such risks involves the assessment of threats, vulnerabilities, and consequences. Assessments are conducted to identify and evaluate potential threats, recognize weaknesses that may be exploited by identified threats, suggest countermeasures to address those weaknesses, and determine which structures or processes are relatively more important to protect from attack. The characterization of security risk is completed through qualitative or quantitative analysis of the consequences associated with the partial or total loss of critical transportation assets because of intentional harmful attacks. Formal methodologies for assessing and managing risks to transportation security provide a conceptual structure and practical tools for allocating resources in cost-effective ways to improve public safety.