Flood damage to road networks primarily manifests as a loss of transportation functionality. Current analyses of road network functionality loss during floods are based on specific flood scenarios. This study analyses flood risk to road networks by assessing the probability of stability loss for various vehicle types (SUVs/emergency vehicles, and cars). Eventually, a flood risk map of the road network is generated. The flood risk of each road is computed as reduced accessibility, measured in this paper via isochrones. Bristol (UK) is used as the case study area, with all hospitals as starting points to study the coverage area of emergency vehicles within a given time frame. The results indicate that road network functionality for SUVs/emergency vehicles has a lower flood risk than that for cars. Additionally, the city centre of Bristol exhibits a higher flood risk, hindering emergency medical vehicles from reaching high-risk flood areas. The findings of this research offer strategies to mitigate the impact of floods on road networks and prepare emergency medical services before flood disasters occur.

This study proposes a methodology for assessing the impact of flood-induced functional disruptions on urban road networks through an agent-based traffic simulation. Network functionality is altered by reducing roads’ free-flow speeds using a risk-based approach, and traffic is appraised considering agent-based traffic dynamics. MATSim, an open-source transport simulator, is employed to model dynamic traffic redistribution and congestion under both baseline (non-flood) and flood conditions of the urban road transportation network. The methodology is applied to the city of Bristol, UK, which is chosen for its complex road layout and flood susceptibility. Key indicators, including travel speed ratios, redistribution ratios, changes in agent count, and time-based isochrones, are used to assess variations in congestion and accessibility under both baseline and flood conditions. This study further advances existing approaches by comparing the spatial shifts of congestion hotspots before and after flooding, and by integrating hazard scenarios to predict potential future congestion patterns and their subsequent impacts on the accessibility of critical facilities, such as the Bristol Royal Infirmary. Results indicate a substantial redistribution of traffic from flood-affected minor roads to central arterial routes, leading to increased congestion and reduced accessibility, which can be particularly detrimental to emergency services that require rapid access to affected areas. The findings highlight the importance of simulating agent-level behavioural responses to network disruption caused by flooding and provide a transferable framework for assessing urban transport resilience during flood events.

Flood hazards can affect road networks by closing roads, extending travel distances and lengthening travel times. This paper innovatively integrates flood hazard, road network topology and vehicle vulnerability via a severity factor to assess the accessibility of exposed links and the performance of the whole network. The overall network functionality loss under different flood return periods is assessed by evaluating the functionality of each network link for cars and SUVs. The most vulnerable links are identified and used to assess the performance of the entire network using topology-based metrics such as average shortest paths and isochrones. The case study of Bristol (UK) is investigated. It is demonstrated that network status is a function of vehicle typology, with SUVs exhibiting naturally stronger resistance to flood than cars. This finding can support preparedness strategies of road networks in the face of future flood events.

Digital Twins (DTs) are forecasted to be used in two-thirds of large industrial companies in the next decade. In the Architecture, Engineering and Construction (AEC) sector, their actual application is still largely at the prototype stage. Industry and academia are currently reconciling many competing definitions and unclear processes for developing DTs. There is a compelling need to establish DTs as practice in AEC by developing common procedures and standards tailored to the sector's procedures and use cases. This paper proposes a step-by-step workflow process for developing a DT for an existing asset in the built environment, providing a proof-of-concept case study based on the Clifton Suspension Bridge in Bristol (UK). To achieve its aim, this paper (i) reviews the state-of-the-art of DTs in Civil Engineering, (ii) proposes a working DT-based workflow framework for the built environment applicable to existing assets, (iii) applies the framework and develops of the physical-virtual architecture to a case study of bridge management, and finally (iv) discusses insights from the application. The main novelty lies in the development of a versatile methodological framework that can be applied to the broad context of civil infrastructure. This paper's importance resides in the knowledge challenge, value proposition and operation dictated by developing a DT workflow for the built environment, which ultimately represents a relevant use case for the digital transformation of national infrastructure.