Safety in numbers
In 2003 P. L. Jacobsen compared rates of walking and cycling, in different countries. Jacobsen looked at the rates of collisions between motorists and cyclists or walkers. He found an inverse relationship. He used a  concept called 'behavioural adaptation' to explain this.  The concept says that drivers who are exposed to more  cyclists on the road begin to drive more safely around them. Though an attractive concept for cycling advocates, it has not been empirically validated. Other combined modelling and empirical evidence suggests that while changes in driver behaviour might still be one way that collision risk per cyclist declines with greater numbers, the effect can be easily produced through simple spatial processes similar to the biological herding processes described above.