# Smartphone Sensors in Motion: Advancing Traffic Safety with Mobile Technology
## 1 Introduction  
Accurately measuring vehicle deceleration is crucial for evaluating traffic safety and the performance of braking systems. Traditionally, this has been achieved using specialized instruments like accelerometers, which provide the precise data needed to enhance vehicle dynamics and safety features. These instruments are the standard in certification and safety tests, ensuring the highest levels of accuracy and reliability. However, the rise of smartphone technology presents a viable alternative. Modern smartphones are equipped with advanced accelerometers and gyroscopes capable of recording acceleration and deceleration values. In some cases, these embedded sensors can match the performance of dedicated measuring devices. There are several instances where utilizing smartphones for this purpose is both practical and advantageous, for example:  
* In educational and training settings, smartphones can be utilized for a variety of purposes, including teaching traffic safety and the physics of vehicle movement. Students can gain practical experience in the principles of deceleration measurement without the need for expensive specialized equipment. * In the initial stages of research, where the need for extreme accuracy is not paramount, smartphones can serve as a cost-effective data collection tool. This enables researchers to rapidly collect and analyze data before resorting to more sophisticated and costly equipment. * In the event of a traffic accident or other emergency, smartphones can provide immediate data on vehicle deceleration, which can be useful for analysis and decision-making before the arrival of professional teams and equipment (e.g., experts in road transport). This study is motivated by the potential of smartphones to serve as cost-effective and easily accessible tools for measuring vehicle deceleration. The primary objective is to assess the accuracy and reliability of smartphones in various conditions, including dry, wet, and gravel roads. Additionally, we aim to compare the performance of smartphones with traditional decelerometers and provide a comprehensive analysis of their effectiveness in real-world scenarios. In the field of brake system testing and methodological studies, various innovative techniques and tools have recently been explored to evaluate vehicle performance under different conditions. [PERSON] et al. [1] evaluated the braking systems of intercity buses through both dynamic and stationary tests, finding that dynamic tests, although more complex, provide a more accurate reflection of real-world capabilities compared to the faster and safer stationary tests. Meanwhile, [PERSON] and his colleagues [2] presented a mathematical model to improve the accuracy of traffic accident analysis by estimating vehicle stopping distances, which integrates different methodological approaches and shows promising validation results. In another study by [PERSON] et al. [3], they proposed an adaptive system that estimates the coefficient of friction between the tire and the road using data from tire-road interaction during emergency braking, using a self-learning neuro-fuzzy system to increase the reliability in traffic accident investigation. [PERSON] et al. [4] evaluated the accuracy of various devices used in dynamic vehicle testing, highlighting the accuracy of a specially designed 5 th wheel device compared to other technologies such as GPS and accelerometers. Finally, [PERSON] and [PERSON] [5] compared traditional decelerometer equipment with a new method of video analysis, finding a strong correlation between the two when measuring braking parameters, suggesting that video analysis could be a cost-effective alternative for educational purposes or in scenarios where specialized equipment is lacking. The literature on brake system modifications and performance analysis shows significant advances in vehicle safety technology and brake system optimization. [PERSON] et al.