Years ago my friend said that if it wasn't for a problem with his foot, a school would have made him walk (or get driven by somebody) to a school that is 1.6 miles away and requires crossing multiple major streets. Regardless of distance, I think there should be a federal law that students should automatically be provided bus transportation if there is a busy enough street between their house and school. In addition, having to walk to school requires students to wake up earlier, and although I can't prove this I think making students walk to school would hurt those students' performance on first period tests and increase the lateness rate.
My high school's bus distance rule was 1.5 miles or more and you got free transportation. Inside 1.5 miles you could apply for free transportation and if there were open seats on a bus route near your house you would get free transportation. Not sure what the cost was if you were denied. My K-5 school did not have a bus service. I think the longest walk was under a mile and there were no busy streets to cross. Junior High, 6-8 did not have buses either which was kind of odd because some students could be 2 miles away and have to cross two busy streets. I loved walking to and from school