# Smart Roads for Autonomous Accident Detection and Warnings
## 3 Proposed Accident Alert Light and Sound System
### A Way to Smart Roads (SRs)  
SRs are roads that have some sort of sensing power given with the help of different types of transducers (devices that convert one form of energy to another) as well as control devices with communication capabilities. Several nodes are installed on the sides of the road to enable sensing at those points. By increasing the number of nodes, sensing power can improve. These nodes hold all the necessary sensing devices and a microcontroller board with a wireless communications system. The distance between nodes is directly proportional to the transmission power of the sensing devices. SRs do not discriminate among vehicle types, and can detect accidents involving Evs as well as nEVs. Similarly, SRs generate light and sound alerts that can be seen and heard by drivers and passengers of approaching vehicles. A smart road has sensing capabilities for accident and/or event detection. A two-way road is shown in Figure 2, each side with AALS nodes which are installed at a distance of 50 m apart. Labels A, B, C, etc., denote the sensing nodes, and each node communicates with neighboring nodes. If a sensor of node D detects an accident, it sends a message to its immediate downstream node, i.e., node C, which will send the received message to node B, and this procedure is repeated until the message finally reaches the EOC. Similarly, on the other side of the road, if an accident is detected by node Y, it sends a message to node X, which relays the message to its previous immediate node, i.e., node W. This procedure is repeated until the message reaches the EOC. A message cannot be received by any node other than its immediately adjacent node. For example, if node D senses an accident, the message is sent to C, B, A, and the EOC. Different channels are used to perform this type of communication. Each channel is in the 400 kHz bandwidth range. To avoid overlapping signals, the immediately adjacent node should be a part of five channels. The transmitting channel and baud rate of one node are similar to the receiving channel and baud rate of its previous adjacent node. For example, if channel 20 is selected for the transmission of a message for node C, then the same channel (i.e., 20) should be selected for node B and other previous adjacent nodes. Figure 1: Proposed algorithm for an AALS node. A functional block diagram of a node in the proposed AALS system is shown in Figure 3.  
Approximately 4000 nodes are required to cover a 100-km two-lane road. Each node has the ability to sense and recognize an accident from loud sounds or obstacle detection by using its different sensors. The Arduino Uno microcontroller takes input from the IR, microphone, smoke sensors, and the HC-12 receiver. A smoke sensor is used to detect fire. When a sound is generated due to an accident between vehicles or by a vehicle hitting an object, the microphone picks up the sound and sends it to the microcontroller, which compares the level with a preset threshold. It declares an accident if the level is higher than the threshold. However, if the sound is not greater than the threshold, the microcontroller discards it. In the meantime, the IR sensor works in parallel to detect obstacles on the road. The microcontroller compares the IR value to check whe  
Figure 3: Block diagram of a node in the proposed AALS system. Figure 2: Illustration of a smart road. set threshold and if the elapsed time is more than five seconds (the time taken by a long vehicle to pass in front of the IR sensor at 20 km/h). When an obstacle remains for more than five seconds, the microcontroller recognizes it as an accident. Meanwhile, if the smoke sensor detects any smoke in the atmosphere, the value of the fire bit changes to HIGH. The controller executes three actions if an accident is detected.