"A University of Colorado Denver study examining collisions between bicycles and motorists, shows bicyclist safety significantly increases when there are more bikes on the road, a finding that could be attributed to a 'safety in numbers effect,'" according to an article on PhysOrg.
"The researchers wanted to create safety performance functions (SPFs) for bicycles in Boulder. SPFs model the mathematical relationship between the frequency of crashes and major factors related to them. Yet while there are SPFs for vehicles, there are none for bikes."
"The authors created their SPF for Boulder by studying crashes at intersections throughout the city where more than two-thirds of collisions occur. They compared the crash data to bicycle count data."