This study evaluated the effects of image preprocessing techniques on detection of Fire Department Connection (FDC) in road view images using a YOLOv8s-based framework. Six preprocessing techniques were applied under identical training and evaluation settings, and their performances were assessed using precision, recall, mAP@50, and mAP@50–95. Geometric correction produced the largest improvement, increasing mAP@50–95 from 0.419 to 0.543 and also improving recall, indicating enhanced localization and detection stability. HSV (Hue, Saturation, Value)-based red restoration achieved the highest average precision among color-based methods, whereas Retinex-based illumination correction degraded the performance across all metrics. Bottom-region cropping improved localization accuracy but reduced recall owing to limited spatial coverage. These results demonstrate that distortion mitigation and selective color enhancement are effective preprocessing strategies for robust FDC detection in road view environments. The study provides practical guidelines for intelligent road asset management, contributing to optimized road network operation and accessibility by reducing emergency vehicle positioning time in complex urban road environments.