In his landmark 2003 paper, Safety in numbers: more walkers and bicyclists, safer walking and bicycling, Peter Jacobsen found that accident rates involving motor vehicles and bicyclists/pedestrians decrease as the number of bicyclists and pedestrians on the road increase. From the Abstract:
Results: The likelihood that a given person walking or bicycling will be struck by a motorist varies inversely with the amount of walking or bicycling. This pattern is consistent across communities of varying size, from specific intersections to cities and countries, and across time periods.
Discussion: This result is unexpected. Since it is unlikely that the people walking and bicycling become more cautious if their numbers are larger, it indicates that the behavior of motorists controls the likelihood of collisions with people walking and bicycling. It appears that motorists adjust their behavior in the presence of people walking and bicycling. There is an urgent need for further exploration of the human factors controlling motorist behavior in the presence of people walking and bicycling.
Conclusion: A motorist is less likely to collide with a person walking and bicycling if more people walk or bicycle. Policies that increase the numbers of people walking and bicycling appear to be an effective route to improving the safety of people walking and bicycling.
It’s a common misconception that increased bicycling and walking will lead to higher injury and fatality rates. The Jacobsen study successfully debunks this myth while providing a potent tool for advocates in their efforts to improve conditions for bicyclists and pedestrians.