Have you ever heard of a walking school bus? Students in some parts of the United states travel by such buses every day. The "driver" of these buses is often a parent who leads a group to and from school-on foot. If the group is large, there is usually another adult who acts as the "conductor" and walks at the rear of the group to make sure that everyone stays to together. Students are picked up and dropped off at their homes. Walking buses help students get fresh air, and they also help reduce pollution and traffic congestion.