The Brooklyn Bridge wasn’t made to handle thousands of pedestrians…. you’d think that the weight wouldn’t be that much different than the weight of a whole bunch of cars, but apparently the vibrations caused by people stepping randomly and shifting their weight are very different from the vibrations of motor vehicles. So during the recent blackout, the bridge started swaying and groaning during the mass exodus. Comforting.
Also blackout-related: How New York City Papers Published in the Dark.