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Safety in numbers is the theory 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.

Examples of safety in numbers include flocks of birds and shoals 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 cyclist if more people walk or bicycle. A Public Health Consultant has concluded that the theory is correct, based on statistical analysis of collision data[1]. 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[2].

After cycling was promoted in Finland, the number of trips increased by 72% and there was a 75% drop in cyclists deaths[3]. Motor vehicle traffic decreased by 16%, bicycle use increased by 28% and cyclist injuries decreased by 20% after the London Congestion Charge began[4]. While such data shows a degree of correlation, conclusions of causality may very well be based on a statistically spurious relationship.


  1. Jacobsen, P. L. (2003). Safety in numbers: more walkers and bicyclists, safer walking and bicycling. Injury Prevention 9 (3): 205-209.
  2. Forester, John Does Increasing the Number of Cyclists Reduce the Accident Rate?. (html) Review of Safety in Numbers.
  3. Saari R. (2005). Cycling policy in Finland and relevance of CBA for the policy. In: CBA of Cycling. Copenhagen, Nordic Council of Ministers, 556.
  4. Transport for London (April 2005). Congestion Charging: Third Annual Monitoring Report..

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