# Smart Disaster Response in Vehicular Tunnels: Technologies for Search and Rescue Applications
## 1 Introduction  
In most parts of the world, with the advancement of industry, urban infrastructure is continuously increasing and developing. In the process of urban expansion, the numbers of tunnels on railways and roads are increasing each year, and the traffic volume of vehicles and people is also increasing. In recent years, the construction of long-distance tunnels with a length of more than 1 km has been rapidly increasing to connect cities and to provide smooth transportation. However, along with the increasing number of tunnels, car accidents in tunnels are also occurring more frequently. In particular, in the case of a fire caused by a car accident in a tunnel, the risk is extremely high because the space is limited and isolated from the outside. The greatest dangers are the smoke and high temperatures that accompany fires, which can cause large-scale casualties. In addition, unlike in above-ground structures, fires inside tunnels are very difficult to extinguish for the following reasons: toxic gas generation by incomplete combustion, difficulty in ventilation of combustion products, unexpected changes in air flow direction, confusion regarding the direction of evacuation, and so forth. The Gottard tunnel fire in Switzerland is an example of this type of accident. The Gottard tunnel is a 16.918-km-long structure that carries two-way traffic. It is recognized as a dangerous tunnel in which an average of 4 fires occur annually. On 24 October 2001, approximately 1 km from the south exit, two trucks caught fire after a head-on collision; 11 people were killed, and 28 people were reportedmissing. In addition, the smoke spread rapidly, and 9 people suffocated. In the case of the Mont Blanc tunnel fire, on 24 March 1999 at 10:46 a.m., a leading driver's cigarette butt flew into the air intake of a refrigerated truck loaded with 9 tons of margarine. At 10:50 p.m., although the visibility dropped by more than 30%, the vehicle continued to run, ignoring the sensor warning, and the truck exploded in 52 min. The driver abandoned the vehicle and informed the control center through an emergency call. However, the exact location of the accident could not be confirmed due to the inability to identify the closed-circuit television camera (CCTV) video data. In addition, the tunnel fire brigade arrived in 57 min, but due to dense smoke, access was difficult, and many casualties occurred. As illustrated by these cases, if a large-scale fire accident occurs in a tunnel, not only loss of vehicles but also large-scale personal injury may occur. In addition, it is necessary to close the tunnel for a long time from accident to recovery, and the social and economic impact is also severe. In this paper, we propose a method for rapid localization of vehicles and victims and decision making of fire fighters for sustainable search and rescue activities at an accident site where smoke is rapidly filling the tunnel from the initial fire or heat source. We also propose a novel search solution and application using various sensors and Internet of Things (IoT) technology. We make the following assumptions regarding a concrete accident environment: (1) clear visibility cannot be secured due to thick smoke in the space surrounding the fire; (2) normal illumination is impossible due to disruption of the power supply; (3) there may be many victims in the closed space including inside of vehicles; (4) the search range is wide and a long time for search and rescue is required; and (5) a search for missing person is needed after the end of the initial disaster response. The main contribution of the proposed system lies in judging and propagating the internal situation accurately and quickly even in emergency fire situations. To this end, the proposed system is classified into three types of response: initial situation detection and propagation using IoT sensor, robot operation for securing visibility in smoke, and localization of fire brigade.