Update date: April 17, 2026
Traffic restrictions are in place on National Route 158 (near Nagawado Dam) due to construction work on the Shin-Iriyama Tunnel.Restrictions will be lifted at 3:00 PM on Friday, April 24, 2026.It is scheduled to happen.
After the restrictions are lifted, the Shin-Iriyama Tunnel and Iriyama Tunnel 2 will be two-way traffic, and Iriyama Tunnel 1 will be one-way traffic, just as before the construction.
Current restrictions (until 3 PM on April 24th)
- Shiniriyama Tunnel:Road Closed
- Iriyama Tunnel ① and ②:One-way alternating traffic all day.(Including Saturdays, Sundays, and public holidays)
Traffic controllers are stationed at the site. Please follow the signs and instructions of the controllers to ensure safe passage.
Project Overview
The Shin-Iriyama Tunnel construction project involves excavating and widening an existing tunnel that branches into a Y shape underground near the Nagawado Dam, and constructing a new tunnel (tunnel length L=410m).
▼ For more details, please check the Nagano National Highway Office website.
Status of construction on the Shin-Iriyama Tunnel, part of the Nagawado Improvement Project on National Route 158 (Ministry of Land, Infrastructure, Transport and Tourism)
*Please note that the schedule may change depending on the progress of the construction work.
