Transportation system security can be defined as the freedom from intentional harm and tampering that affects both motorized and nonmotorized travelers, and may also include natural disasters. Security goes beyond safety and includes the planning to prevent, manage, or respond to threats of a region and its transportation system and users.
Awareness of both man-made and natural security concerns has increased in recent years due to events like September 11, 2001 and Hurricanes Katrina and Rita. The vulnerability of the transportation system and its use in emergency evacuations are issues receiving new attention. Transportation planners have been encouraged to focus on security interrelated issues and to initiate the consideration of security within their transportation planning and programming activities