## 2 Literature Review
### Risks in Bridge Projects  
Risk is defined as an event with known uncertainty, measured by its probability and severity of impact. It has the potential to significantly affect project outcomes, including cost, time, scope, and quality, and can be perceived individually or collectively, with both negative and positive impacts on project goals [40; 41; 42; 43; 44; 45; 46; 47; 48; 49]. Often overlooked, risk and uncertainty play a crucial role in the sustainability challenge, particularly in economic analyses of sustainable development [50]. Risk management is essential to decision-making and is integrated into the structure, operations, and activities of an organization at strategic, operational, program, and project levels. It involves systematically applying rules, procedures, and practices to communication, context definition, risk assessment, treatment, monitoring, review, and reporting. Researchers classify risks as internal, external, environmental, economic, social, financial, market, safety risks, etc., which vary by project size, type, and scope. Effective risk management is vital to mitigating these risks and achieving time, cost, quality, safety, and environmental sustainability goals. It enables project teams to make timely decisions by identifying, classifying, quantifying, managing, and controlling risks, balancing the effort to manage risks with the resulting benefits in a cost-benefit analysis to maximize project value [41; 42; 44; 48; 49; 51; 52]. The complexity of bridge projects exposes them to a wide range of interconnected risks that significantly impact project lifecycles. Numerous studies have highlighted these risks, categorizing them into different categories that influence project success. A systematic review of 26 studies identified key risks in bridge projects that can be mitigated or managed using Building Information Modeling (BIM), grouping them into environmental, economic, and social categories. Common challenges include information management, document automation, structural maintenance, and resource allocation throughout the bridge project. Environmental risks involve selecting climate-appropriate eco-friendly materials and managing carbon footprints. Economic risks encompass communication gaps, inaccuracies in cost and schedule planning, and inefficiencies in execution monitoring. Additional economic challenges include supply chain disruptions, productivity issues, and organizational problems. Social risks cover safety evaluations, community engagement,and team organization [4]. Furthermore, a meta-analysis of 21 studies on bridge projects in China found that safety risk factors often stem from interconnected sources, including environmental conditions, materials, technical aspects, management practices, and personnel. Environmental risks, such as extreme weather and natural disasters, can disrupt construction. Technical risks are related to design flaws and construction errors, while management risks stem from poor planning and inadequate oversight. Personnel risks impact project outcomes through safety and skill level issues, while bridge-specific risks require tailored management strategies to ensure safety and functionality [53]. Additionally, a study analyzing 23 papers identified risks categorized as internal (project-specific challenges like environmental and management practices) and external (broader factors like natural hazards and economic impacts). The analysis covered environmental, economic, and social impacts on communities, stakeholder satisfaction, and structural adequacy under varied conditions. Other highlighted risks include natural hazards, political threats, congestion, land acquisition issues, and internal management conflicts. This research underscores the need for comprehensive risk management strategies to address the diverse and interconnected risks in bridge projects [54].