Risk Assessment of Bridges and Analysis of Road Traffic Scenarios through Traffic Simulation

This study focuses on bridge risk assessment and the analysis of alternative road network scenarios by using traffic simulation methods. The primary objective of the research is to assess the risk associated with the Neochori–Katochi Bridge and to analyze alternative road network scenarios in the event of partial or total loss of its serviceability, particularly due to seismic events. The bridge is located at the Municipality of the Sacred City of Messolonghi, in the Regional Unit of Aetolia-Acarnania, western Greece, and constitutes a critical link in the local and regional road network. The study area corresponds to the expanded Municipality, with approximately 32,000 inhabitants, comprising the municipal units of Messolonghi,Aitoliko and Oiniades. The Oiniades unit, with about 9,000 inhabitants, hosts the Neochori–Katochi Bridge, which lies along a provincial road and serves as a key connection for daily commuting, freight transport and regional accessibility. The bridge has an approximate length of 190 m and is located at coordinates 38.4094° N, 21.2605° E. Given its strategic importance, any disruption would have significant social and economic impacts to the wider area. To address these issues, an integrated methodological framework was applied, combining seismic, traffic and behavioural analyses. Data collection included traffic flows, speeds and geometric characteristics of the road network, as well as structural and seismic information related to thebridge. In parallel, a questionnaire-based survey was conducted among residents and drivers of the surrounding areas to capture travel behaviour and route choice preferences under both normal and disrupted traffic conditions. Based on seismic hazard maps previously developed for the study area, our analysis evaluates the seismic risk and functional importance of the bridge. Secondly, multiple traffic management and network reconfiguration scenarios are developed to represent potential conditions after loss of bridge serviceability. These scenarios include alternative routing strategies designed to accommodate displaced traffic flows while minimizing traffic congestion and travel delays. Traffic microsimulation models areused to analyse and compare the proposed scenarios. The evaluation focuses on key performance indicators such as volume to capacity ratios (v/c) and travel delays. Specific attention is given to the ability of the surrounding road network to absorb rerouted traffic without severe degradation of operational conditions. Moreover, the questionnaire survey data are analysed using discrete choice models, in order to identify the factors that influence drivers’ selection of alternative routes. Variables such as travel time, perceived safety, reliability and road characteristics are examinedto understand how users adapt their behaviour in response to local network disruptions. Overall, the current research offers a comprehensive approach to bridge risk assessment that goes beyond structural considerations by focusing on traffic performance and road users’ behaviour. The findings support the development of more resilient road network planning strategies and could assist in practical guidance for emergency traffic management and long-term infrastructure improvement in seismically active regions.