The Tunnel of Folgoso is located on the A-52 highway in Pontevedra, in the northwest of Spain. It enhances the road communication between the central plateau and the region of Galicia. It is a 2.5 51-metre-long unidirectional twin-tube tunnel. It was opened in 1998, With a traffic intensity of 3750 vehicles per day.17.2% of those are heavy vehicles. Traffic of heavy good vehicles through the tunnel is permitted, as well. In 2006, a project design for tunnel refurbishment was undertaken in accordance with the Spanish standard for safety in road tunnels (Royal Decree 635/2006). The refurbishment works began in 2008, keeping the tunnel within operation. The tunnel of Folgoso is the longest highway tunnel in Spain that has been revamped to meet RD 635/2006 requirements. There has been a wide renovation of equipment concerning electrical systems, lighting, ventilation, firefighting and communications, mainly. The tunnel is a pioneer in deploying some features. For instance, it is the Spanish longest highway tunnel with fluorescent lighting, and the first to be endowed with an anti-glaring system. This device avoids the risk of the drivers to be glared by the sunlight, due to the tunnel's east-west orientation. Besides, a new Tunnel Control Centre of great architectural value has been built, perfectly merged with the environment. The building hosts the whole equipment that is needed for the tunnel's control and monitoring, as well as the offices for thg personnel in charge of the maintenance and exploitation. Several challenges were undertaken during the works, since the tunnel remained in operation. Risk analyses were done taking into account different ways to divert traffic through one tube and a county road, in order to assess whether or not the safety conditions of the tunnel were high enough to ensure a reasonable safety level. Another hindrance for the works raised when the electrical supplier stated that the whole electrical power demand couldn't be provided. Thus, an electrical optimization study was developed in order to suit electrical demand and protocols to the actual power supply. All these circumstances altogether bring out the tunnel of Folgoso as a notorious and referential tunnel in Spain.