In the near future in Washington , D.C., at the beginning of rush hour, a highway overpass collapses. An ominous cloud of dust billows and drifts towards the city.

Commuters panic, wondering if they are exposed to a radioactive or biological agent. An emergency radio broadcast describes a detour to get everyone off the highway quickly. Some commuters have weather radios stashed in the back seat that automatically turn on and broadcast the same message. Those at home watching television see the alert crawl across the bottom of the screen; those still in the office receive an email or pop-up window. Cell phones and pagers ring with automated voice mail and text messages. People are advised to stay indoors until the nature of the dust cloud is known, to check into a hospital if they feel ill, and to call a hotline with any information about the collapse. Read More »