Only 13.5% of the traffic deaths were pedestrians and bicyclists in this study http://en.wikipedia.org/wiki/Car_crash#Common_types_of_collision http://en.wikipe

Only 13.5% of the traffic deaths were pedestrians and bicyclists in this study http://en.wikipedia.org/wiki/Car_crash#Common_types_of_collision http://en.wikipedia.org/wiki/Car_crash#Common_types_of_colli... whereas the main causes of death are stroke and heart attack http://en.wikipedia.org/wiki/File:Causes_of_death_by_age_group.png http://en.wikipedia.org/wiki/File:Causes_of_death_by_age_gro... both of which are to some extent prevented by exercise. So it seems probable that parents who stop their children walking to school are more likely to kill them than save their lives.