Critical Infrastructure Renewal: A Framework for Fuzzy Logic Based Risk Assessment and Microscopic Traffic Simulation Modelling

This paper presents a comprehensive framework for risk assessment and micro simulation modelling to assess traffic impacts during re-decking of a major suspension bridge identified as Critical Infrastructure (CI) in Halifax, Canada. The bridge is being replaced while maintaining traffic during day time. As re-decking is relatively a rare and unknown construction event for a Cable Bridge, unexpected risk event and uncertainty would be associated with complex engineering manoeuvring during the re-decking of the bridge. Therefore, this study proposes a fuzzy logic approach to estimate the construction related bridge opening delay, and subsequently develops a micro simulation-based traffic network model to assess the traffic impacts on transport network. Weather data, traffic volume and signal data obtained from multiple data sources have been used during the risk assessment and micro simulation modelling. The results suggest that the likelihood of bridge opening delay could range from 18%-30% for an hour period to 40% for 3 hour period depending on the level of consequence on any day in December. The average potential delay is obtained as 22 minutes, 1.5 hours, and 2.6 hours for low consequence, medium consequence, and high consequence respectively. Based on the delay analysis, this study evaluates three alternative bridge opening delay scenarios. It is observed that the increment in number of operating vehicles becomes steady at 30% suggesting the network has reached its capacity. The results also reveals that any delay over 2 hours in bridge opening would add a slight change to the impacts on the network. This study will help policy-makers to develop risk mitigation plans and contingencies to ensure better management of traffic during 18 months long re-decking of this critical infrastructure.