1 Roles and Implications of Transportation Systems in Homeland Security
Virginia Department of Transportation, Richmond, Virginia
High Street Consulting Group, Pittsburgh, Pennsylvania
In the United States, state Departments of Transportation (DOTs), working with agencies at the local and federal governmental levels, have responsibility for planning, delivering, operating, and maintaining a vast surface transportation network that includes not only four million miles of roads serving local, regional, and national travel needs , but also many rail lines, bus and rail transit systems, ferries, ports, and waterways. The emergency preparedness capabilities that public-sector transportation agencies are acquiring are critical to safe and efficient operation of the nation's transportation network in the twenty-first century.
Surface transportation is uniquely positioned among critical infrastructures and key resources in terms of its management by agencies with broad policy responsibility, public accountability, large and distributed workforces, heavy equipment, communications infrastructure, and ability to directly and swiftly take action (akin to the private sector). This institutional heft and continuous programmatic investment provide a stable base for a campaign to systematically reduce risk exposure over time through hazards capital budgeting.
Whether moving by car, truck, bus, train, ferry, bicycle, or on foot, Americans depend on surface transportation for safe and predictable mobility. On trips through town or across the country, vehicles drive an estimated eight billion miles on roads in the United States every day  and a considerable share of daily travel is associated with moving the estimated 89% of all freight by value that is shipped on highways .
The apparent scale and redundancy of the nation's transportation network gives a false sense of security, but in many parts of the country that network is straining to keep up with the transportation demands of society and the economy. A single unexpected interruption in one location may have a dramatic ripple effect on travel across a wide region.
In August 2007, for example, the collapse of Minnesota's busiest bridge (I-35W) that carried 140,000 vehicles a day over the Mississippi River between downtown Minneapolis and its northern suburbs, not only caused tragic loss of life, but is also expected to have an economic impact of about $60 million in road user detour costs incurred before it is fully replaced  at an expected cost of at least $393 million. The US Department of Transportation estimates that there are at least 1000 bridges across the country where substantial casualties and economic disruption would result from isolated terrorist attacks .
Homeland security is one among many threats to safe and efficient operation of the nation's transportation network. An act of terrorism at a busy bottleneck or malevolent destruction of a major bridge would almost certainly cause unacceptable loss of life and temporary disruption of economic stability and necessitates costly infrastructure repairs. Historically, a range of threats, such as floods, earthquakes, extreme weather, wildfires, or major traffic incidents, have all proven capable of generating similarly adverse outcomes.
As travel grows with economic prosperity, lower density land use, and more mobile populations, incidents of any kind pose greater potential to disrupt the transportation network. Transportation agencies have no choice but to enhance their emergency preparedness capabilities to ensure that they can meet five fundamental responsibilities :
1. prevent incidents within their control and responsibility; 2. protect transportation users, agency personnel, and critical infrastructure;/di