The I-35W Bridge collapse occurred before the advent of Twitter, when there were only 50 million users of Facebook (as February 2012 there were 845 million users, and growth in user numbers seems to be leveling off). [I joined Facebook on November 13, 2004, so they tell me, when Facebook had fewer than 1 million users (Facebook User Growth Chart by Ben Foster)], but it was pretty much useless to me until late 2008 when enough people I knew were on to make it interesting to check in. And though I added 24 “friends” in 2007, I never posted. It did not even occur to me to update my Facebook status, which would likely be the first place many Twin Citians would go today in such an event. I did update my blog the next day.
Yet the news traveled fast. TV, radio, on-road variable message signs, phone calls, emails, all helped transmit this knowledge. We have evidence on how the news traveled by looking at traffic counts. The figure below shows the difference in counts between August 1 and a week earlier, July 25, which are otherwise similar days. As noted, behavior changed quickly that night, traffic counts were lower systemwide, but especially upstream and downstream of the collapse. In contrast the best long distance alternatives (Mn100 and I-35E saw upticks in traffic).