Safety in numbers

Safety in numbers is the hypothesis that, by being part of a large physical group or mass, an individual is proportionally less likely to be the victim of a mishap, accident, or other bad event.

Evidence often advanced for this position includes the flocking of birds and shoaling of fish. In both of these instances, by being part of a large group, individuals face less risk of falling victim to predators than they would if traveling alone.

Safety in numbers is also used to describe the theory that a motorist is less likely to collide with a pedestrian or bicyclist if more people walk or bicycle. A Public Health Consultant has concluded that the theory is correct, based on statistical analysis of collision data. A Cycling Transportation Engineer has disputed that conclusion, writing that the data used is insufficient to demonstrate that there is a cause-and-effect relationship.

After cycling was promoted in Finland, the number of trips increased by 72% and there was a 75% drop in cyclists deaths. Motor vehicle traffic decreased by 16%, bicycle use increased by 28% and cyclist injuries decreased by 20% after the London Congestion Charge began. While such data shows a degree of correlation, conclusions of causality may very well be based on a statistically spurious relationship.