The New York Times has published an analysis of a body of research on playground construction designed to be "safe" and minimize the risk of injury.  The changes include replacing asphalt surfaces with rubber or wood chips, lowering overall play structure heights, and removing see-saws and other equipment that could hurt ankles or cause other injuries.

Researchers have found that while the changes prevent some injuries, they also hold back a key function of playgrounds--to allow children to encounter risks and overcome fears.  Ironically, the researchers conclude, parental fears of injury actually end up having psychological consequences for the children, including overblown anxiety over minor injuries.