Alborz Tunnel, Tehran- Shomal Freeway Implementation of construction operations of Alborz Tunnel in the Tehran-Chalous freeway Status In Progress Alborz Tunnel Geography Location Description The project involves construction of 2 main tunnels and a service tunnel. The service tunnel was excavated by TBM. Alborz main tunnels are the longest road tunnels in Iran with a length of 6400m and cross section of 11.92m. By executing these tunnels the mountainous 12km road is reduced to a 6km rout.