It feels a bit like a double whammy — because as everyone knows, bikes travel far slower than motor vehicles and hold up traffic in general. It's easy for drivers to assume that bikes cause slowdowns, which then cascade into potentially treacherous, backed-up traffic. The researchers completed their study in Portland, Oregon, by some estimates home to some of the worst traffic in the United States. They looked for vehicles following other motor vehicles, and then those that followed cyclists. The researchers plan to expand their study to include a greater variety of roadways, traffic volumes and other variables to see how cyclists affect other types of vehicular dynamics.