Disaster evacuation of the old city of Nicosia

Marios Stylianou, Marios Demetriou, Andreas Aristidou

In Proceedings of the 8th International Disaster and Risk Conference, IDRC 2025, Nicosia, Cyprus, October 22 - 24, 2025.

This paper presents a digital twin–based simulation of evacuation scenarios in Nicosia’s historic walled Old Town, showing how dense urban morphology, gate blockages, and infrastructure changes affect evacuation efficiency and highlighting the need for coordinated, adaptive flow-management strategies to reduce disaster risks in historic cities.

[DOI] [paper] [bibtex]

Historic urban centers face unique evacuation challenges due to their dense morphology, aging infrastructure, and cultural preservation constraints. This study focuses on Nicosia's walled Old Town, a complex environment shaped by 16th-century fortifications, irregular street patterns, and limited access through six operational gates. Using a high-fidelity, geo-referenced digital twin of the area, we simulate evacuation scenarios under various stress conditions, including road closures, gate blockages, and alternative shelter placements, through a hybrid agent-based model built in Unity. Our findings reveal that certain conditions lead to significant evacuation delays, and that uncoordinated infrastructure additions may worsen outcomes without proper guidance mechanisms. This work highlights the importance of coupling infrastructure upgrades with adaptive flow-management strategies and provides an open-source dataset to support future research in disaster risk reduction and crowd dynamics in historic cities.

The main contributions of this work include:

• Enhanced the high-fidelity digital twin of Nicosia’s Old Town by integrating geographic road network data and a hybrid agent-based model to enable real-time evacuation scenario testing and stakeholder engagement.
• We present a hybrid agent-based simulation framework that models pedestrian and vehicle dynamics using Unity’s AI Navigation system, enhanced with custom behavioral logic.
• We conduct a series of evacuation experiments to evaluate system performance under stress, quantifying clearance times, congestion hotspots, and shelter saturation effects.

The authors would like to thank the i-Nicosia project team for providing the 3D models of the old city of Nicosia as part of the digital twin concept.