The Gimry Road Tunnel is the longest road tunnel.

The Gimry Road Tunnel is the longest road tunnel in Russia. Located in Dagestan, it connects Buynaksk and the village of Gimry, providing the shortest and weather-independent transport link for the construction of the Irganay Hydroelectric Power Station, as well as connecting nine districts of mountainous Dagestan with the railway and the republic's center. The length is 4,303 meters. The capacity of the Gimry Tunnel is 4,000 vehicles per hour. The roadway width is 7 meters, and the clearance height is 5 meters.

The tunnel is situated within layers of limestone, sandstone, aleurolite, and argillite at a depth of up to 900 meters from the surface. The tunnel cross-section diameter is 9 meters, with a roadway width of 7 meters. The longitudinal profile of the tunnel is double-pitched, sloping from the middle towards the portals. Parallel to the tunnel runs a service drainage and ventilation adit (connecting cross-passages are located every 300 meters). The tunnel is illuminated and equipped with automatic fire alarm systems, security alarms, loudspeaker notification, telephone communication, television surveillance, operational ventilation, and central dispatch control.

The tunnel was constructed to facilitate the delivery of materials for the erection of the Irganay hydroelectric complex, funded by the latter's budget. Excavation from the northern portal began on December 31, 1979, and from the southern portal in 1983.

Construction was carried out under challenging climatic and geological conditions; most of the cargo for the southern portal was delivered by water transport via the Chirkey Hydroelectric Power Station reservoir and then by road. The work at the northern portal was led by Leonid Petrovich Parasyuk. The breakthrough of the tunnel faces was achieved in 1991; since then, the tunnel has been in temporary operation. Before the main tunnel breakthrough, traffic was conducted through the ventilation adit, for which transitions from the main shaft were equipped.

Due to the incomplete construction, the tunnel was in unsatisfactory condition: the vaults were not properly reinforced, and groundwater seeped through. In December 2007, when a counter-terrorist operation regime was introduced in the village of Gimry, the tunnel was closed to traffic. Since the mid-2000s, reconstruction work on the tunnel has been underway. The final commissioning was initially scheduled for 2010, later postponed to 2011 (with 1.7 billion rubles planned for construction work in the tunnel that year), and then to September 2012.

After reconstruction, the Gimry Road Tunnel was officially opened on October 2, 2012.

As a strategic road linking Makhachkala with the mountainous regions, the Gimry Tunnel attracted heightened attention from terrorists. In particular, a major terrorist attack near the tunnel was prevented in October 2005.

Sources:

https://ru.wikipedia.org/wiki/Gimry_Road_Tunnel

https://welcomedagestan.ru/placepost/gimrinskij-avtodorozhnyj-tonnel/