A new  study finds that bike sharing is actually safer than riding your own bike. 

The studier build of the shared bikes and casual riding style of their renters could contribute to the greater safety of bike sharers, said researcher Elliot Martin at the Mineta Transportation Institute.

"The vehicle-involved collision rate of bike-sharing systems we evaluated is generally lower than established metrics of collision rates and injury rates of personal cycling," Martin said.

Bob Prevedi of the Bicycle Coalition of Philadelphia said his group is not surprised at the study results.

He compared the rental bikes to a rental car.

"The whole adage about rental cars and people beating them up is actually wrong," he said. "I think people, in general, try to treat things that they are renting more carefully and more considerately."

The study also found that bike-sharing riders don't wear helmets as much as other riders, which could result in more careful cycling.

Philadelphia started its bike-sharing program about a year ago.