Bridge Failures and their Causes: A Narrative Review of Structural, Environmental, and Human Factors

Bridges are critical components of transportation networks, yet catastrophic collapses continue to occur, sometimes in structures that were previously judged acceptable by conventional inspection and evaluation practices. This narrative review synthesizes bridge failure mechanisms reported between 1970 and 2024 and organizes them into structural, environmental, and human-organizational domains. The synthesis indicates that environmental hazards frequently act as the immediate trigger, with hydraulic scour repeatedly emerging as a dominant initiating mechanism, while severe outcomes are often enabled by latent vulnerabilities such as deterioration, limited redundancy, constructability and inspectability limitations, and gaps in inspection, communication, and maintenance decision-making. By integrating failure case evidence with reliability and lifecycle perspectives, the review highlights how capacity declines over time can intersect with changing demands and extreme events, increasing the likelihood of rapid, disproportionate collapse. The paper also discusses climate non-stationarity as a growing challenge for hazard characterization and emphasizes opportunities for proactive asset management through enhanced monitoring, data integration, and decision-support tools. The proposed synthesis framework supports more consistent failure attribution and informs strategies for resilient design, inspection planning, and risk-based maintenance policy.