Global transportation infrastructure exposure to the change of precipitation in a warmer world

Reliable transportation infrastructure is crucial for international trade and economic stability. However, it's increasingly threatened by natural hazards, particularly extreme weather events exacerbated by global warming. Increased intensity and frequency of extreme precipitation events are expected to lead to infrastructure deterioration, higher maintenance costs, and disruptions. Achieving Sustainable Development Goal 9 (resilient infrastructure) requires understanding and mitigating these climate impacts. While previous research has focused on direct and indirect economic damage from climate-related events, little attention has been paid to adapting design standards to account for changing climate conditions. This study addresses this gap by analyzing how the probability of extreme precipitation events will change globally and how design standards need to be adjusted to maintain infrastructure reliability.

The literature highlights the significant economic losses from natural hazards impacting transport infrastructure. Studies estimate global multi-hazard risk to roads and railways in the billions of USD. Research shows a clear link between rising global temperatures and increased intensity and frequency of extreme precipitation events. While there's extensive work on the direct economic damage to infrastructure and indirect losses from network disruptions, there's a lack of research on necessary changes to design standards to mitigate future climate extremes. This study aims to fill this gap and inform climate adaptation strategies.

This study uses multi-model projections from the Coupled Model Intercomparison Project Phase 5 (CMIP5), specifically the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) dataset, with a spatial resolution of approximately 25 km × 25 km. The analysis assesses changes in precipitation return periods between the baseline period (1971–2000) and future horizons (2030–2059 and 2070–2099) under RCP4.5 and RCP8.5 scenarios. The generalized extreme value (GEV) distribution was fitted to annual maximum daily precipitation (RX1day) data to estimate precipitation intensity for different return periods. Infrastructure data was obtained from OpenStreetMap (OSM), categorizing roads (motorways to tertiary roads) and railways. Countries were grouped into four income categories (World Bank classifications) to assign different design return periods for drainage systems. The study then calculated absolute exposure (total length of assets experiencing a >25% decrease in design return period) and relative exposure (ratio of absolute exposure to total assets within a grid). A safety factor for climate change adaptation was introduced, representing the ratio of future to present precipitation intensity for the design return period. This factor helps determine adjustments needed in design standards.

The analysis reveals that 91.7–94.6% of the global landmass is projected to experience decreasing precipitation return periods (increased frequency of extreme events). Under RCP4.5, 58.7% (mid-21st century) and 73.8% (late-21st century) of the world will experience a >25% decrease in return periods; under RCP8.5, these figures rise to 71.5% and 86.6%, respectively. Significant decreases are projected for regions including Greenland, North and South America, Central Africa, the Siberian Plateau, Central India, Southwest China, and Southeast Asia. Regarding infrastructure exposure, 88.4–94.6% of global transportation assets will have shorter design return periods. Under RCP4.5, 6.8 million km (mid-century) and 11.0 million km (late-century) of assets will be exposed to more frequent extreme precipitation (>25% return period decrease); under RCP8.5, this increases to 10.3 million km and 16.5 million km, respectively. The United States and China show the highest absolute exposure, primarily due to high infrastructure density in exposed regions. Relative exposure analysis reveals that many less-developed countries, even with fewer assets, face high vulnerability. A safety factor analysis suggests that a factor of 1.2 is sufficient for most regions under RCP4.5 for quick design calculations, but a higher factor is necessary under RCP8.5, particularly in India, Southwest China, Southeast Asia, East Africa, and the Andes.

The findings highlight the widespread vulnerability of global transportation infrastructure to increased precipitation extremes. The significant decrease in design return periods underscores the need for incorporating climate change into infrastructure design and planning. The geographical distribution of exposure reveals hotspots needing prioritized adaptation measures, helping direct resource allocation efficiently. While the study provides a global overview, local-scale analyses are crucial for implementing specific adaptation strategies. The proposed safety factor provides a practical tool for adapting design standards, but it's important to consider the trade-offs between cost and risk reduction.

This study demonstrates the substantial and geographically varied exposure of global transportation infrastructure to changes in extreme precipitation. The proposed safety factor provides a practical approach for incorporating climate change into infrastructure design. Prioritizing adaptation measures in identified hotspots is crucial for effective resource allocation. Future research should explore the cost-effectiveness of different adaptation strategies and integrate diverse approaches for optimal risk reduction, considering local factors and uncertainties.

The study relies on several assumptions, including consistent design standards within countries and the accuracy of OSM data. The analysis does not consider all factors affecting infrastructure resilience, such as maintenance practices and material quality. The focus is on precipitation; other climate-related hazards affecting infrastructure were not directly analyzed. Finally, the cost-benefit analysis of different adaptation measures was not performed.