# Real-Time Performance Measurement Application via Bluetooth Signals for Signalized Intersections
## 2 Materials and Methods
### Bluetooth-Based Traffic Analysis Detector
In addition, the presence of many Bluetooth devices in a busy area (e.g., mobile phones, and in-car Bluetooth systems) can cause signal congestion. Environmental factors also affect Bluetooth signals. Weather conditions such as heavy rain, snow, or high humidity can affect Bluetooth signal strength. Although Bluetooth traffic analysis sensors can effectively collect data under suitable conditions, they can encounter various interferences that affect the propagation of the signal. In order to minimize the effect of these interferences, the designed Bluetooth traffic analysis sensors are placed in suitable locations. In addition, appropriate frequency management techniques are used in the designed sensor and additional software and hardware solutions are implemented. Various strategies and solutions are implemented to minimize the effect of interferences in the designed Bluetooth traffic analysis sensors. There is Adaptive Frequency Hopping Spread Spectrum (AFH) in the designed sensor. Adaptive Frequency Hopping Spread Spectrum (AFH) ensures that the Bluetooth signal constantly changes frequency in the 2.4 GHz band. In this way, frequencies that create interference are detected and skipped, and communication is established over less intense frequencies. Thus, interferences are reduced, signal stability is increased, and data transmission is made more reliable. Bluetooth technology can skip frequencies 1600 times per second. This fast-hopping reduces the possibility of devices conflicting with other devices using the same frequency band. Another part used in the sensor to reduce interferences is the high-power antenna. The antenna used in the designed sensor is optimized and placed to increase the signal power. The effect of obstacles is reduced with the high-gain antenna. In the designed method, signal fusion is performed by using multiple sensors. In other words, after receiving the MAC address of a Bluetooth device passing through any direction of the intersection, this MAC address is detected and matched in any of the Bluetooth devices in the other directions. Thus, false data caused by interference are prevented. The designed Bluetooth sensor is designed in a case with a high degree of protection. Thus, the sensor is protected from environmental conditions such as extreme weather conditions and physical impact. Apart from using Bluetooth signals, there are various techniques for real-time performance measurement at signalized intersections. One of these is inductive loop detectors. Inductive loop detectors are widely used and provide reliable data about vehicle presence and passage. They are cost-effective for long-term use. However, they have a costly maintenance process. Inductive loop detectors require an installation by closing the traffic during the application. They are also limited in their ability to capture detailed data such as vehicle speed or class. Another performance measurement technique is video image processing. Video image processing systems provide comprehensive data including vehicle numbers, speeds, and classifications. They can cover multiple lanes and provide high-accuracy real-time data. However, these systems are expensive to install and maintain. They can also be adversely affected by environmental conditions such as fog, rain, or poor lighting. One of the techniques used in performance measurement is infrared sensors. Infrared sensors are effective in measuring queue lengths and vehicle speeds. However, these sensors are sensitive to environmental factors such as extreme temperatures or heavy rain, which negatively affect their accuracy. They also have a limited detection range compared to other methods. Another technique used in performance measurement is radar-based systems. Radar systems provide accurate data on vehicle speed, distance, and direction. They are effective in various weather conditions and can cover more than one lane at a time. Radar systems are costly and their accuracy can be affected by large metal objects or other interferences in the environment.