Remember that old driving school advice that bridges freeze before roads? Well, it's true (and it happens because bridges lose heat from both above and below, unlike roads, which are insulated by the earth), and it's a major problem for highway officials who want to ensure safe driving for their communities. Every winter, trucks are out before dawn carefully applying sand, salt, and deicing solution, depending on the region, to bridges and overpasses to make sure they're safe to drive on.
In Seattle, the road maintenance director decided that it would be a good idea to get a jump on the freeze by applying de-icer at noon to one of the city's many overpasses. Unfortunately, the Seattle concrete didn't take well to the application. Instead, the de-icer created a slick surface that was actually more dangerous than the ice itself, leading to several minor car accidents. Lesson learned: de-icer needs time to work before the road is driven!