The Americans with Disabilities Act (ADA) is a civil rights law, which prohibits discrimination on the basis of disability. In 2000, the Architectural and Transportation Barriers Compliance Board issued a final rule in the form of accessibility guidelines to serve as the basis for standards adopted by the Department of Justice for new construction and alterations of play areas by the ADA.
These guidelines were adopted into law in 2010. As of March 15, 2011 all play areas should be in compliance with these guidelines.
For further information contact http://www.access-board.gov/
NPPS has a CD-ROM the offers clear explanation of the ADA standards for play areas.