# Smart Disaster Response in Vehicular Tunnels: Technologies for Search and Rescue Applications
## 4 Experiments and Discussion  
### Temperature and Smoke Experiments  
It is important to understand the characteristics of tunnels, especially regarding heat and smoke, so that the search and rescue equipment developed in this study can be effectively used in the actual field. For this purpose, a fire dynamic simulator (FDS) [42] was used to analyze the fire behavior in the tunnel. The experimental conditions of the tunnel were assumed to be 1 km in length, 4.5 m in height, and 13 m in width. In the simulated fire situation, one car was burning in the center of the tunnel, and the temperature inside the tunnel was set to 10 \({}^{\circ}\)C with 1 atm. The outside temperature was set to 15 \({}^{\circ}\)C. The condition of the fire source had a heat release rate (HRR) of 2500 kW, and the size of the fire source was set to 3 \(\times\) 2 \(\times\) 0.5 m. Experiments were carried out to measure the changes in temperature and smoke over time. The results are shown in Figure 15 and 16. As seen in Figure 15, the heat is not easily diffused and the temperature rises to a maximum of 450 \({}^{\circ}\)C at a height of 10 m above the source of the fire. In addition, it can be seen that the temperature rises to 300 \({}^{\circ}\)C near the ceiling above the fire source. This means that for the initial search operations, a robot or fire brigade can reach the fire up to 10 m distance without heat protection equipment. Of course, if the fire brigade is equipped with heat resistant clothing or equipment, it is possible to reach a fire source up to 1 m distance. However, when a vehicle fire spreads to a large number of neighboring vehicles, the amount of heat generated is further increased, and the temperature is expected to increase sharply.  
Figure 16 shows the behavior of smoke over time under the same conditions as in Figure 15, and smoke diffusion was not observed at 50 s after ignition. At 350 s, the visible distance of about 200 m from the ignition point was about 9 m, and when 900 s had elapsed, the visible distance to the vicinity of 320 m in both directions was confirmed to be about 9 m. This means that as the fire brigade's input would be delayed; the smoke would spread and it would become very difficult to perform search and rescue operations. However, if an IR camera is used, images can be transmitted through the smoke, so it would not be difficult to locate the fire and victims. Figure 17 shows that this is possible in an environment with an actual visibility distance of 9 m or less. Although it is not possible to identify a fire point by a conventional camera, an IR camera accurately recognizes a fire point. Table 2 summarizes the fire recognition performance of the vision system proposed in Section 3.2.  
Figure 15: Temperature distribution in tunnel.  
Experiments were carried out to determine whether the fire alarm was successfully generated and the recognition ratio according to the distance between the fire point and the camera, illumination (day, night), fire type (gasoline, heptane, wood). Experimental results show that the alert message is successfully transmitted in all cases, and the recognition ratio is higher as the distance from the fire spot is closer and the surroundings are darker.