"In just a few generations, we have tightly restricted American kids' freedom to roam, play, and become self-sufficient. The percentage of children walking and bicycling to school has plummeted from almost 50 percent in 1969 to about 13 percent today. Although distance from school is often cited as the main barrier to walking and bicycling, many families still drive when schools are close to home. According to the Safe Routes to School National Partnership, driving accounts for about half of school trips between 1/4- and 1/2-mile long — which in most cases shouldn't take kids much more than 10 minutes to walk."
Via Seth Dixon