Object detection in resource-constrained environments poses challenges for real-time intelligent transportation systems (ITS), where low resolution, compression artifacts, and bandwidth limitations hinder performance. This study evaluates YOLOv8, YOLOv10, and YOLOv12 on the Poribohon-BD dataset of 15 native Bangladeshi vehicle classes using three dataset variants: resized images, JPEG-compressed images (Q50, Q75), and GAN-enhanced images restored with Real-ESRGAN. The results show that resolution is the dominant factor, and YOLOv8 delivers the most stable performance under all conditions. YOLOv10 generalized slightly better at very low resolutions, while YOLOv12 was competitive at higher resolutions under compression and GAN restoration but degraded at lower scales. GAN enhancement improved accuracy only when there was sufficient base resolution, revealing a gap between perceptual fidelity and detection accuracy. Overall, these findings provide a systematic framework for selecting YOLO architectures and preprocessing pipelines under degraded inputs, supporting deployment in real-world ITS.