I have heard some criticism of Jacobsen’s 2003 study that showed that, for cyclists, there was safety in numbers, but it’s good to see a couple of other studies that seem to validate it.
The phenomenon, dubbed “safety in numbers,” was first identified in 2003, in an academic paper by public health researcher Peter Jacobsen [PDF]. After being asked by officials in Pasadena, Calif., if their city “was a dangerous place to bicycle,” Jacobsen began looking at crash data from various communities where bicycle ridership had fluctuated over time.
What he found surprised him: The number of crashes involving bikes correlated with the number of riders in a community. As ridership fluctuated, so did the crash rate. More riders, fewer crashes; fewer riders, more crashes.