"In 1969, 48 percent of children 5 to 14 years of age usually walked or bicycled to school (The National Center for Safe Routes to School, 2011). In 2009, 13 percent of children 5 to 14 years of age usually walked or bicycled to school (National Center, 2011). In 1969, 41 percent of children in grades K–8 lived within one mile of school; 89 percent of these children usually walked or bicycled to school (U.S. Department of Transportation [USDOT], 1972). In 2009, 31 percent of children in grades K–8 lived within one mile of school; 35 percent of these children usually walked or bicycled to school (National Center, 2011)."

[Source](http://guide.saferoutesinfo.org/introduction/the_decline_of_...)