Using closed-circuit television cameras to analyze traffic safety at intersections based on vehicle key points detection

In the within-intersection area, vehicles from different approaches make turning movements resulting in many conflict points. Hence, drivers are more prone to make mistakes in that area, which leads to severe crash outcomes. In the current roadway system, the Closed-Circuit Television (CCTV) cameras could be a cost-effective sensor to monitor the safety condition in the within-intersection area. This study proposed a framework named "Near Miss Event Detection System (NMEDS)" for road safety diagnostics using video data collected from CCTV cameras. The proposed framework combined the Mask-RCNN bounding box detection and Occlusion-Net detection algorithm to reconstruct vehicles' key points in a 3D view. Vehicles' key points including right-front headlight, left-front headlight, right-back taillight, and left-back taillight could be identified and transformed into a 2D bird's-eye view (i.e., real-world coordinate system) for safety analysis. A method was proposed to modify the occluded key points, which could not be observed by cameras due the turning movements in the within-intersection area. The post-encroachment time (PET) was calculated by using the trajectory data in the 2D view. The proposed framework was compared with two counterparts (i.e., bounding box detection only and key point detection only) by conducting an empirical study at a 4-leg intersection. The results suggested that the proposed framework could obtain more accurate vehicle trajectory and better autocorrelation analytics was conducted to identify the significantly dangerous locations in the within-intersection area. It is expected that the proposed methods could help diagnose road safety problems using CCTV cameras. Moreover, the proposed method could be incorporated with Connected Vehicle Systems and provide information to nearby drivers based on Infrastructure-to-Vehicle (I2V) technologies.