Eyes on the Road: A Hands-Free Speed Alert System

Abstract

Driving over the speed limit remains a major contributor to road traffic accidents globally, with the World Health Organization estimating that it accounts for nearly 30% of road fatalities. This study presents the design and implementation of a microcontroller-based speed monitoring and alarm system aimed at alerting users when a preset speed threshold is exceeded. The system simulates vehicle speed using a rotating fan, whose speed is continuously monitored using a Hall effect sensor. An Arduino Uno microcontroller processes the signal, displays the real-time speed on an Organic Light Emitting Diode (OLED) screen, and activates an audible buzzer alarm when the simulated speed exceeds the defined limit. Once the speed drops below this threshold, the buzzer is automatically deactivated. The system was tested under various conditions, including dynamic speed simulation to verify real-time responsiveness, threshold sensitivity and display accuracy checks to ensure reliable measurement, and alarm response time evaluation to confirm prompt triggering. The measured speed readings closely matched those from  Amprobe TACH-20 Non-Contact Handheld Tachometer, with deviations consistently within ±0.5 m/s. The alarm system activates just above the defined 60 m/s threshold and includes a controlled hysteresis window of 2.05 m/s to avoid false triggering. Response time measurements showed an average latency of 9.99 ms, with a maximum delay of 16.66 ms. These results confirm that the system operates accurately, consistently, and promptly under simulated conditions.