## 4 Discussion and Future Research Directions
### Future Research Directions
The whole system approach involves integrating multiple models and approaches to address the problem of how to facilitate the indirect impacts of flooding on transportation as a whole. Subsequently, network modifications could be provided to decrease flood impacts on transportation systems. Additionally, it is still unclear whether strengthening a few critical links can reduce the overall impact of floods on traffic and more research is required on this issue. * Analyzing the larger spatial scales: The scarcity of data, uncertainties, and assumptions in modeling techniques make flood and traffic modeling at larger spatial scales more challenging. It is not specified whether it is possible to apply regional traffic models to national-level analysis. Because of daily technological advancements (e.g., availability of mobility data) and computational power, it is expected that the indirect flood impacts prediction of large-scale disruption scenarios become comparatively easy. While future transportation disruption modeling will become more complex and challenging due to the deployment of emerging technologies, such as Connected and Automated Vehicles (CAV) in future mobility systems, cybersecurity issues, and the growing frequency and magnitude of floods. * Addressing the interdependency modeling: The transportation system is closely connected to other critical infrastructures, such as power and communication networks. Interdependency modeling considers the interconnectedness of these different systems. Although interdependency modeling is a new concept in transportation planning, it will become increasingly important in future transportation system analyses. As information technology and related infrastructure become more essential to transportation systems, they must be considered in an integrated and multidisciplinary context, specifically in case of disruptions, such as flooding situation. The vulnerability of energy infrastructure, such as power outages, must also be addressed. * Evaluation of other specific traffic parameters: This review reveals that the majority of scholarly literature on the indirect impacts of flooding on transportation systems, published since 2005, has focused on improving the resilience of transportation systems and addressing road networks. As described in Section 3, most of the publications examined in this review concentrated on changes in the travel time of passenger vehicles. In addition to the commonly studied traffic factors identified in this system atic literature review, certain other specific parameters have also been explored as indicators of resilience, including reliability, restoration time, and capacity [12]. These parameters can be employed in future research to evaluate the indirect impacts of flooding on transportation. * Evaluating the results of the studies: In assessing the studies included in this review, the aim was not to provide a summary of their results, as this was not pertinent to the research questions being investigated. Nevertheless, it can be assumed that the analyzed papers meet an acceptable standard of validation and accuracy, given that they are peer-reviewed articles. To properly summarize the findings in this area, the accuracy of the models could be further examined in future research. * Noting the hybrid methods' limitations: Regarding hybrid methodologies, it is crucial to carefully select and construct the considered parameters and variables. To achieve this goal, it is essential to consult with as many stakeholders as possible when developing the models. Although hybrid methods have made a valuable contribution in predicting the indirect impacts of flooding on traffic, there are still several challenges to overcome to maximize their impact. For instance, as each model needs to be parameterized, reliable data, specifically travel behavior data, is necessary. However, obtaining this kind of data can be challenging due to its sensitive and private nature.