When bike share programs first began gaining popularity in the U.S. about a decade ago, they were the target of numerous safety concerns. Encouraging inexperienced bikers to navigate unfamiliar cities without a helmet sounded like a recipe for disaster, but bike sharing has since proven to be even safer than riding a bike of your own. According to a new study reported by Vox, the possible explanations for this may be just as surprising as the phenomenon itself.

There are 21 deaths for every 100 million cycling trips in the U.S., and when looking at bike share trips alone that number drops down to zero. Not only are you less likely to die while riding a public bike, but the new report from researchers at the Mineta Transportation Institute [PDF] shows that collision and injury rates are also lower in at least three cities.

The authors of the study suggested a few reasons for this trend, some of which have been used by critics to argue against the safety of bike sharing in the past. A rider's lack of experience, for instance, may actually end up working to his advantage. According to experts interviewed by the research team, less-experienced bikers also tend to be more cautious and risk-averse.

One of the most important factors that contributes to the safety of bike sharing is likely the bike itself. Bike sharing bicycles are heavier and sturdier, which makes them better suited for potholes than the light-weight fixed gears most urban riders own. They usually come in bright, easy-to-spot colors and feature drum brakes that perform better in wet conditions. The slow-moving traffic of cities, where most bike share programs are focused, could also make them less prone to accidents.

Even with the impressive safety numbers, there's a lot cities can still do to encourage commuters to start bike sharing. Portland's bike share program will soon feature bikes that can be locked up anywhere, and London is planning to introduce laser-projecting cycles that illuminate the streets in front of them.

[h/t Vox]