The route includes the Karisaka Tunnel, first opened in 1998 and at 6.225 km (3.868 mi) is the fifth-longest road tunnel in Japan.Because it is the main road connecting Saitama and Yamanashi, both prefectures are developing the Nishikanto Road.[2]
^"一般国道の路線別、都道府県別道路現況" [Road statistics by General National Highway route and prefecture] (PDF) (in Japanese). Ministry of Land, Infrastructure, Transport and Tourism. Retrieved 19 February 2020.