# Smart Disaster Response in Vehicular Tunnels: Technologies for Search and Rescue Applications
## 3 Proposed Disaster Response Systems for Tunnel Accidents
### Robot for Prompt Search  
When a fire occurs in a tunnel, the cause, scale, and location of the accident are accurately confirmed through CCTV, fire sensors, and radar, and this information is transmitted to the control server via the wired or wireless network in real time. If the fire is mild, the fire can be suppressed by the driver himself or herself. However, it usually takes 5 to 10 min for a fire truck to arrive at the scene, so the fire typically progresses rapidly, and smoke and fumes fill the tunnel. In this situation, it is possible to use fans for ventilation, but in small or old tunnels, fan installation may be insufficient. Thus, it is necessary to investigate the internal fire progress in detail because hasty entry may lead to the injury of fire fighters. Of course, it is possible to monitor such a situation remotely through existing CCTV. However, since visibility is rapidly reduced by smoke and there are many blind spots, it is difficult to use existing camera equipment to observe tunnels. To overcome this problem, a robot that can collect information on the hot spot can be utilized in place of a fire fighter. There are various kinds of reconnaissance robots for disaster site deployment, but if a tunnel is longer than 1 km, the robot needs to have an average speed of 50 km/h to reach the fire within 1 to 2 min. For this purpose, a wheel-type ground-based robot is suitable for faster driving, in comparison to the caterpillar type. However, when a large number of  
Figure 8: Architecture of the proposed radar system. vehicles are stuck in a tunnel due to an accident, access is difficult. Of course, if the fire brigade has secured a shoulder or emergency ramp, it will be possible to use a robot. Another option is to use drones to quickly access the fire through the air, regardless of the vehicle's identity. In particular, if the altitude is maintained at a certain height above the vehicles, straight flight is possible without collision with obstacles. It is important not only to have a high-resolution camera, but also to mount an IR camera on the robot to overcome the smoke and locate the fire and victims. Recently, as the drone platform has become popular, low-cost models and camera modules have been developed. In the proposed system, IR and red-green-blue (RGB) cameras are installed in a drone as shown in Figure 9. The photographed image data is directly transmitted to a fire fighter who is operating the drone. The data can also be transmitted to a remote control center through a WiFi-based access point (AP) built into the tunnel or a wireless interface mounted on the controller. However, since the actual transmission distance of WiFi is about 100 m, when multi-hop communication is used in a tunnel of 1 km or more, the throughput is drastically decreased according to the increase of the number of hops. Therefore, in order to smoothly transmit and receive image data in a tunnel of 1 km or more, an analog RF communication method is suitable. The proposed system extends the communication range to more than 1 km by using RF module of 424 MHz. Another consideration is the issue of whether the UAV will receive data from sensors installed in the tunnel and participate directly in the routing procedure. Although it is possible to be developed, it is a problem that the weight of the payload and the battery consumption rate increase due to the addition of the RF of the same specifications as the sensor deployed in the tunnel. Moreover, due to the high mobility of the UAV, the additional handover delay increases. Therefore, the proposed fire response system provides the routing process only among the statically installed IoT sensors, for fast and stable transmission of emergency information considering the particularities of the tunnel. Despite this extended communication distance via analog based RF communication, it is still difficult to use automatic flight, such as the waypoint flight of a drone, because it is impossible to track its position using GPS inside a tunnel.