The start of the May bridge on the A-4, near Dos Hermanas, was marked by a traffic accident that caused significant congestion on the approaches to Seville. This incident not only affected travel times but also exposed critical conflict points in the road's geometry. We analyze the accident dynamics through forensic 3D reconstruction, simulating the interaction between vehicles, traffic density, and emergency response times to document the scene.
Simulation of accident dynamics and road geometry analysis 🚗
For the reconstruction, the A-4 roadway was modeled using cadastral data and orthophotography, identifying the acceleration and deceleration lanes at the exit towards Dos Hermanas. Testimonies indicate a sudden braking before the impact, suggesting an unanticipated speed reduction. Using multibody simulation software, the trajectory of the involved vehicles was recreated, calculating the kinetic energy dissipated in the crash. The simulation reveals that the congestion originated from a domino effect at the tail of the queue, where the lack of safe following distance was a determining factor. Traffic density was visualized in a temporal heat map, showing that the conflict point was located 200 meters from the merge, where the average speed dropped from 90 km/h to 10 km/h in less than 30 seconds.
Lessons for road safety and access improvement 🛣️
The 3D reconstruction shows that the road geometry, with a sharp entry curve and poor vertical signage, contributed to the late perception of danger. It is proposed to simulate the impact of installing variable message panels and intelligent beaconing on that stretch. The visualization of response times, from the alert to the arrival of emergency services (12 minutes), suggests the need to optimize access points for tow trucks. This analysis not only documents the accident but also offers concrete data to redesign the intersection and mitigate future collapses during periods of high demand.
How does the accuracy of the 3D reconstruction influence the determination of the technical causes of the accident on the A-4 during the May bridge?
(PS: In scene analysis, every scale witness is a small unsung hero.)