Robust video-based vehicle speed estimation for occluded scenes for forensic analysis of traffic accidents
摘要
Accurate vehicle speed estimation is essential for forensic traffic accident reconstruction, yet conventional video-based methods typically require prior camera calibration or spatial road data. This study introduces a modular framework that estimates vehicle speed from fixed-camera footage even when parts of the vehicle trajectory are completely occluded, without any prior information about the camera or accident scene. The framework integrates SiamRPN-based single-vehicle tracking with Kalman filtering to handle occlusions and uses Mask R-CNN instance segmentation to extract wheel centers. It then applies a smoothed unscented Kalman filter to predict occluded wheel coordinates and computes vehicle speed from the geometric cross-ratio—a perspective-invariant distance ratio—combined with known wheelbase specifications. Validation across three settings demonstrated high accuracy: simulations on straight and curved roads yielded maximum errors of 0.30 km/h and 1.70 km/h, respectively; real vehicle tests achieved errors of 0.41 km/h under constant-speed driving and 0.57 km/h during acceleration; and actual accident case studies produced errors of 0.49–3.05 km/h compared with field measurements. Unlike existing approaches that provide only point or interval estimates, the proposed framework generates continuous speed profiles throughout the accident sequence, enabling dynamic analysis of driver behavior such as acceleration, deceleration, and braking response. When vehicle specifications are available, this approach delivers legally defensible speed estimates from readily available video evidence, significantly improving the precision and practical utility of forensic accident reconstruction.