ABSTRACT
The surface transportation infrastructure can be characterized in terms of three main components: the physical infrastructure that is made up of roads and pavements, highway systems, bicycle and walking paths, bridges and tunnels, railroads, waterways, and their supporting sub-structures such as signage, street lighting, and traffic signals; the vehicle infrastructure that includes automobiles, buses, trains, and boats, along with their propulsion, fuel, and control systems; and the organizational/institutional infrastructure that is composed of both public and private components, including federal, state and local governments, and agencies that manage surface transportation and private companies that supply the various system components. In the past several decades the digital infrastructure, composed of sensors, controls, communication systems, computers, and data, has become an increasingly indispensable and integrated part of the physical, vehicle and institutional transportation infrastructure.
