ABSTRACT
Components of the Road System –e road system in the United States has three components: paved surfaces on the ground, bridges, and tunnels. Each of these components has diœerent characteristics that make it vulnerable to natural, technological, and human-caused damage, including being a potential target for terrorist attacks. –e road system binds the American economy through drivers commuting to work and the movement of raw materials and goods. Loss
of a road for even a short period of time can be costly. As noted earlier, the earthquake-induced loss of the I-10 corridor in Los Angeles in 1994 “cost the local economy $1 million per day” (U.S. DOT, 2002, p. 33), while the wider economy was impacted through the loss of access to the Port of Los Angeles (U.S. DOT, 2002.)
Road Surface –e paved surface of the road system is constructed of layers topped by asphalt or concrete. –e roadway is engineered to specižcations dictated by safety and e²ciency factors. While “pervious concrete” is now available for use in some applications, thus allowing water to percolate through the paving into the ground, most road surfaces are impervious to water, meaning that drainage elements have to be included in the construction (Figure 5.1). Roads are generally “crowned,” or higher in the middle, to facilitate water runoœ because a sheen of water on the road can interfere with steering and braking and cause “hydroplaning,” where a car’s tires lose contact with the road surface and therefore the driver loses control of the car.
