Blind spot accidents are a major cause of collisions during lane changing and overtaking, particularly in ordinary vehicles that lack advanced driver assistance systems (ADAS). This project presents a cost-effective Smart Blind Spot Detection System using ultrasonic sensors to monitor the area beside and behind the vehicle that is typically hidden from the driver’s field of view. The system employs ultrasonic distance measurement to detect nearby vehicles or obstacles within a defined detection zone and provides real-time alerts through LEDs and an audible buzzer. A microcontroller processes distance data using filtering and hysteresis algorithms to minimize false alarms caused by road boundaries or transient noise. The sensors are positioned on the rear side panels of the vehicle to ensure accurate coverage of the blind spot region. The proposed system enables ordinary vehicles to achieve a level of safety similar to modern BSD systems, reducing lane-change accidents and improving overall driving awareness. The design is simple, low-cost, and suitable for retrofit installation in any conventional vehicle.

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