Figure 1. Location of study schools and major trunk roads in Chiba Prefecture, Japan. A-F schools (closed circles) are located in urban areas, and G-J schools (open circles) are in rural areas. The dotted lines show major trunk roads.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.