A Simulation Study of ST-GNN-Based Risk Warning and Active Visual Guidance for Low-Position Lighting on Bridge Segments

Traffic risks on bridge segments exhibit spatiotemporal dependence under congestion, low visibility, and sudden traffic incidents. This study develops and evaluates a reproducible simulation framework that links short-term risk-proxy forecasting with graded low-position lighting control for a 1200 m linear bridge corridor. The framework uses six traffic and environmental scenario families, a direction-separated graph convolution and gated recurrent unit model, explicit baselines and graph ablations, and a rule-based upstream coordination controller. The model predicts a continuous conflict-exposure proxy for 20 control zones over a five-minute horizon. Across ten training seeds, the proposed DS-GCN-GRU achieved a mean RMSE of 0.1094 ± 0.0004, MAE of 0.0773 ± 0.0007, macro-F1 of 0.8339 ± 0.0082, Level 3 recall of 0.8777 ± 0.0095, and high-risk PR-AUC of 0.9292 ± 0.0010. Real-world safety benefits and driver responses to the proposed lighting commands have not been validated.