Road and railway tunnel fire hazard: a new measurement method for risk assessment and improvement of transit safety

Fire is one of the main causes of trouble in long tunnels and its effects are often severe also because of the smoke and toxic gases produced. Although great care has been posed to develop reliable fire extinguishing systems and safe paths for people escaping from fire, prevention is still considered one of the most effective ways to face the problem. The paper describes a security system developed with the goal of reducing the risk of fire, as much as possible, in both road and rail tunnels. The security system presented is able to monitor the infrared emission of a whole vehicle, both a train and a truck, entering a tunnel. The system is equipped with sensing devices all around the vehicle; the resulting map is then related to the top, the bottom, the side views, the front and the rear, leading to a complete infrared mapping of the vehicle. In the case of a "hot spot", characterized by a temperature higher then a fixed threshold, the software automatically produces an alarm signal and the potentially dangerous vehicle is stopped and carefully inspected. As known, the use of infrared thermometry needs special care regarding a number of aspects, emissivity above all, which are essential in getting reliable measurements; the paper considers some of them. The first application of the developed security system has been installed near the entrance of the Frejus Tunnel, in Italy.