Last summer on Martha’s Vineyard, a 19-year old visitor to the Island lost part of her leg in a moped accident. The incident renewed calls for a closer look at the safety and licensing of moped rentals on the Island. Leading the call is a group called MADAC , an acronym for “Mopeds Are Dangerous Action Committee.” In the studio, Mindy Todd's guests are Nicole Friedler Brisson , one of the founders of MADAC; and Tim Rich , acting police chief of Chilmark, and also a member of MADAC,