The walks are pretty long so the designer, who used to be on a track, team wanted to turn it into a positive:
Photo here:
http://news.mynavi.jp/photo/news/2014/10/31/119/images/002l.jpg
Article here:
http://japanrunningnews.blogspot.com/2015/04/why-is-there-track-in-narita-airport.html